Classic Outlook cannot add Business Premium account — modern sign-in window fails silently

Question

Classic Outlook cannot add Business Premium account — modern sign-in window fails silently

Steven Dealph 20

When adding this account to classic Outlook (Windows), the modern sign-in window attempts to open once per restart, closes immediately without displaying, and Outlook falls back to a legacy dialog: "Problem Connecting to Server — An encrypted connection to your mail server is not available." On repeated attempts without restarting, the modern window no longer attempts to open at all.

Already confirmed/ruled out:

Mailbox fully provisioned in Azure AD and Exchange Online (Remote Connectivity Analyzer — Mailbox Provisioning Test: Passed)
External connectivity confirmed (Remote Connectivity Analyzer — Outlook Connectivity Test: Passed)
Email address verified correct, no typos - Webroot antivirus disabled and retested — not the cause
Windows Credential Manager checked, stale entries cleared
No cached Autodiscover.xml file found locally
Office fully updated (Version 2606, Build 20131.20154)
Office sign-in identity switched to include this account
Full Office Online Repair completed
Stale "Access work or school" registration found and removed
Registry checked: EnableADAL not present/disabled
Registry key added: HKCU\Software\Microsoft\Exchange\ AlwaysUseMSOAuthForAutoDiscover = 1
WebView2 Runtime fully reinstalled and confirmed present (v150.0.4078.99)

None of the above resolved the issue.

Steven Dealph 20 Reputation points

2026-08-07T17:46:20.5+00:00

Wanted to close the loop on this one — your suggestion to try a new Outlook profile turned out to be exactly right, though not quite for the reason we suspected at the time.

Got on a call with Microsoft Support, who identified that several apps (Outlook, Teams, and Word) were silently defaulting to my old MS 365 Home/Personal account instead of the new Business Premium account, even when I thought I was adding the right one. That mix-up appears to have been sitting in my original profile's settings the whole time — a truly fresh test profile I created later in the week actually hit the identical Outlook errors, which is what first suggested this wasn't really about profile corruption. Setting up the new profile is what finally gave me a natural point to notice and correct the account reference, and once that was fixed in File > Add Account, Classic Outlook connected immediately — all accounts and calendars, including a second long-broken client account, came online right away.

So in the end it wasn't New vs. Classic Outlook, or anything tenant/license-side — an account-identity mix-up that was easy to miss because the wrong address looked plausible, and your suggested fix is exactly what surfaced it. Everything is fully working now. Really appreciate the help getting here.

Answer accepted by question author

Dora-T 15,980 Microsoft External Staff Moderator

Hi Steven Dealph

I understand how frustrating this must be, especially after the extensive troubleshooting you've already completed. I truly appreciate the time, effort, and patience you've put into investigating the issue and providing such detailed information.

Before considering the next step, could you please confirm whether you've also tried the following?

Creating a completely new Outlook profile (Control Panel > Mail > Show Profiles > Add) and then adding the account to that new profile.
Creating a new Windows user profile and testing whether the same issue occurs when adding the account from that profile.

If you've already tried both of these steps and the issue persists, I recommend contacting Microsoft Support for further assistance. For further instructions, you can follow this guide: Get support - Microsoft 365 admin | Microsoft Learn.

Please note that we're not Microsoft Support; this is a user-to-user community forum. Moderators here don't have access to your environment or Microsoft's backend systems, so we can only provide guidance based on public documentation and community experience.

Thank you for your patience and understanding.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Steven Dealph 20 Reputation points

2026-07-27T04:00:03.01+00:00

Thanks for the thoughtful reply! To clarify: yes, the account was added to a brand-new Outlook profile created specifically for this (not an existing one) — the failure happened on that fresh profile. I haven't yet tried a separate Windows user profile to test in isolation — I'll try that and report back but that only eliminates one other issue and doesn't really help me access the software.

I purchased an upgrade last Tuesday because I have a client that needs to me use one of the tools. I spent much of last week trying to get it to work and after much navigation, found it to be a "failed" purchase (I got an email receipt and everything!). Every attempt to connect with any information that could help me failed. I was even hung up on twice by some automated system that I was directed to. Finally, I purchased it again but spent all weekend trying to get it to work.

Thank you for the suggestions and I will try the second one tomorrow but will the link you provided above really get me to someone (or something?) that can help me get this resolved?

Sorry for any frustration. Its been a long week and weekend. I do appreciate your response and will follow up.

Thanks!
Steven Dealph 20 Reputation points

2026-07-27T04:07:49.8133333+00:00

Dora-T. See my reply above. When I try to respond to you it froze so I tried to exit and come back in. Must have replied in the wrong spot. Sorry.
Dora-T 15,980 Reputation points Microsoft External Staff Moderator

2026-07-27T05:01:15.4333333+00:00
Hi Steven Dealph

Thank you for your update, and I appreciate you taking the time to clarify the troubleshooting you've already completed.

The link I shared is for submitting a support request through the Microsoft 365 admin center. If you have a Microsoft 365 Global Administrator account, you can create a support request by following these steps:

Sign in to the Microsoft 365 admin center using your Microsoft 365 Business administrator account.

Select the Help & support (headset) icon.

If Support Assistant is enabled, turn it off.

Type contact support in the search box.

Select Contact support, then choose Phone or Email to submit your request.

Once you've submitted the request, Microsoft Support will contact you using the contact method you selected.

Please let me know the results after you've tested with a new Windows user profile as well.

Thank you again for your patience, and I hope you're able to get this resolved soon.
Steven Dealph 20 Reputation points

2026-07-31T05:02:12.9766667+00:00

Dora T- Update as of July 30, 2026 at 9:59 pm

Thank you for the earlier guidance on isolating this issue.

I've completed a definitive test based on your suggestion to try a fresh Outlook profile: I created an entirely new Windows user profile and tested Outlook there.

Results:

• Microsoft 365 Business Premium mailbox: Connected successfully on first attempt ✓

• Exchange Online modern authentication: Working perfectly ✓

• Calendar functionality: Fully functional ✓

• Enterprise client account (broken since June): Also connects successfully in the new profile ✓

• Email send/receive: Working as expected ✓

Conclusion:

Since the same Outlook version and account connect without any issues in a fresh Windows profile, but fail in my original profile, the root cause is definitively a Windows user profile-level issue—not a tenant configuration, license problem, or Outlook version issue.

The corrupted profile appears to be triggering conflicts with the modern authentication sign-in process at the Windows system level.

Resolution:

I'm migrating to the fresh Windows profile as my primary work environment this weekend, which will resolve the issue.

Thank you for pointing me toward this diagnostic approach—it provided the clarity needed to identify and fix the problem. By the way, while I first approached this because we couldn't get the new MS 365 Pro suite to work, it also seems to have resolved an issue I have had since the beginning of June (2 months!) with my clients enterprise email/calendar suddenly not working. You are a lifesaver! Thank you!

Best regards,

Steven Dealph

1 additional answer

Your answer

Steven Dealph 20 Reputation points

2026-08-07T17:46:20.5+00:00

Wanted to close the loop on this one — your suggestion to try a new Outlook profile turned out to be exactly right, though not quite for the reason we suspected at the time.

Got on a call with Microsoft Support, who identified that several apps (Outlook, Teams, and Word) were silently defaulting to my old MS 365 Home/Personal account instead of the new Business Premium account, even when I thought I was adding the right one. That mix-up appears to have been sitting in my original profile's settings the whole time — a truly fresh test profile I created later in the week actually hit the identical Outlook errors, which is what first suggested this wasn't really about profile corruption. Setting up the new profile is what finally gave me a natural point to notice and correct the account reference, and once that was fixed in File > Add Account, Classic Outlook connected immediately — all accounts and calendars, including a second long-broken client account, came online right away.

So in the end it wasn't New vs. Classic Outlook, or anything tenant/license-side — an account-identity mix-up that was easy to miss because the wrong address looked plausible, and your suggested fix is exactly what surfaced it. Everything is fully working now. Really appreciate the help getting here.
Steven Dealph 20 Reputation points

2026-07-27T04:00:03.01+00:00

Thanks for the thoughtful reply! To clarify: yes, the account was added to a brand-new Outlook profile created specifically for this (not an existing one) — the failure happened on that fresh profile. I haven't yet tried a separate Windows user profile to test in isolation — I'll try that and report back but that only eliminates one other issue and doesn't really help me access the software.

I purchased an upgrade last Tuesday because I have a client that needs to me use one of the tools. I spent much of last week trying to get it to work and after much navigation, found it to be a "failed" purchase (I got an email receipt and everything!). Every attempt to connect with any information that could help me failed. I was even hung up on twice by some automated system that I was directed to. Finally, I purchased it again but spent all weekend trying to get it to work.

Thank you for the suggestions and I will try the second one tomorrow but will the link you provided above really get me to someone (or something?) that can help me get this resolved?

Sorry for any frustration. Its been a long week and weekend. I do appreciate your response and will follow up.

Thanks!
Steven Dealph 20 Reputation points

2026-07-27T04:07:49.8133333+00:00

Dora-T. See my reply above. When I try to respond to you it froze so I tried to exit and come back in. Must have replied in the wrong spot. Sorry.
Dora-T 15,980 Reputation points Microsoft External Staff Moderator

2026-07-27T05:01:15.4333333+00:00

Hi Steven Dealph

Thank you for your update, and I appreciate you taking the time to clarify the troubleshooting you've already completed.

The link I shared is for submitting a support request through the Microsoft 365 admin center. If you have a Microsoft 365 Global Administrator account, you can create a support request by following these steps:

Sign in to the Microsoft 365 admin center using your Microsoft 365 Business administrator account.

Select the Help & support (headset) icon.

If Support Assistant is enabled, turn it off.

Type contact support in the search box.

Select Contact support, then choose Phone or Email to submit your request.

Once you've submitted the request, Microsoft Support will contact you using the contact method you selected.

Please let me know the results after you've tested with a new Windows user profile as well.

Thank you again for your patience, and I hope you're able to get this resolved soon.
Steven Dealph 20 Reputation points

2026-07-31T05:02:12.9766667+00:00

Dora T- Update as of July 30, 2026 at 9:59 pm

Thank you for the earlier guidance on isolating this issue.

I've completed a definitive test based on your suggestion to try a fresh Outlook profile: I created an entirely new Windows user profile and tested Outlook there.

Results:

• Microsoft 365 Business Premium mailbox: Connected successfully on first attempt ✓

• Exchange Online modern authentication: Working perfectly ✓

• Calendar functionality: Fully functional ✓

• Enterprise client account (broken since June): Also connects successfully in the new profile ✓

• Email send/receive: Working as expected ✓

Conclusion:

Since the same Outlook version and account connect without any issues in a fresh Windows profile, but fail in my original profile, the root cause is definitively a Windows user profile-level issue—not a tenant configuration, license problem, or Outlook version issue.

The corrupted profile appears to be triggering conflicts with the modern authentication sign-in process at the Windows system level.

Resolution:

I'm migrating to the fresh Windows profile as my primary work environment this weekend, which will resolve the issue.

Thank you for pointing me toward this diagnostic approach—it provided the clarity needed to identify and fix the problem. By the way, while I first approached this because we couldn't get the new MS 365 Pro suite to work, it also seems to have resolved an issue I have had since the beginning of June (2 months!) with my clients enterprise email/calendar suddenly not working. You are a lifesaver! Thank you!

Best regards,

Steven Dealph

Answer 1

Thanks for the thoughtful reply! To clarify: yes, the account was added to a brand-new Outlook profile created specifically for this (not an existing one) — the failure happened on that fresh profile. I haven't yet tried a separate Windows user profile to test in isolation — I'll try that and report back but that only eliminates one other issue and doesn't really help me access the software.

I purchased an upgrade last Tuesday because I have a client that needs to me use one of the tools. I spent much of last week trying to get it to work and after much navigation, found it to be a "failed" purchase (I got an email receipt and everything!). Every attempt to connect with any information that could help me failed. I was even hung up on twice by some automated system that I was directed to. Finally, I purchased it again but spent all weekend trying to get it to work.

Thank you for the suggestions and I will try the second one tomorrow but will the link you provided above really get me to someone (or something?) that can help me get this resolved?

Sorry for any frustration. Its been a long week and weekend. I do appreciate your response and will follow up.

Thanks!