Selected Personal account accidentally for Microsoft 365 business and now the rest of the 4 people cannot use their outlook anymore. How to fix this ?

Question

Hi,

The Microsoft 365 subscription is associated with my company's business account only.

In signing into one of my colleague's computer, I accidentally chose the "personal account" instead of "IT group". Subsequently she accepted the License change and then afterwards, the rest of us cannot use our outlook.

I tried to reverse that by logging out of all Microsoft account and remove all Microsoft accounts:

I also reboot the computer and try to sign-in again:

When I click the sign-in, I am redirected to the login screen where I can enter my email address.

It prompted "It looks like this email is used with more than one account from Microsoft. Which one do you want to use?"

I chose the "IT group", but no matter what, it cannot be switched back to business even though we have paid for the subscription for 5 PCs. Please see error message below:

AADSTS500200: User account

Request Id: [Moderator note: personal info removed]

Correlation Id: [Moderator note: personal info removed]

Timestamp: [Moderator note: personal info removed]

Message: AADSTS500200: User account '[Moderator note: personal info removed]' is a personal Microsoft account. Personal Microsoft accounts are not supported for this application unless explicitly invited to an organization. Try signing out and signing back in with an organizational account.

How can I solve this situation?

Thank you for your support.

Answer 1

As this forum is a public platform, we’ve taken steps to help protect your privacy by removing your organization’s domain name from your message. To ensure your data remains secure, we kindly recommend avoiding the inclusion of personal or organizational details such as domain names or screenshots with sensitive information in future posts.  

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Hi @Raymond Gwee, 

Thank you for reaching out to the Microsoft Q&A forum and for clearly outlining your concern. 

Based on the details you shared that Outlook stopped working for four colleagues after a personal account was chosen during sign in and you now see error AADSTS500200 even though you have an active Microsoft 365 Business subscription. I truly understand and appreciate the effort you have already made to sign out everywhere, remove accounts, reboot, and try again. 

This occurs because the same email address is currently recognized as two separate identities with Microsoft, a personal Microsoft account and a work account in your organization. When the personal identity is selected, Microsoft 365 Business apps cannot activate and they display the prompt asking which account you want to use, followed by the AADSTS500200 message indicating that personal accounts are not supported for that application. Moreover, Microsoft documents that personal accounts cannot perform tenant administrative actions and are routed to a Microsoft services tenant, which reinforces the separation between personal and organizational identities that you are encountering. 

Below are some alternative steps designed to address your situation effectively: 

1/ Clear cached sign in data and credentials on each affected computer 

• First close all Office apps.  
• Next sign out from within an Office app by opening Word or Outlook and going to File then Account.  
• Then remove stale Office and Microsoft 365 entries in Windows Credential Manager.  
• After that run the Microsoft Support and Recovery Assistant to reset Office activation and sign in so the next prompt uses the correct organizational identity.  

If any device still loops, repair the Windows Account Manager broker packages that handle modern authentication and restart the computer. These steps refresh local tokens and typically restore Outlook connectivity.  

2/ Sign out the personal identity and sign back in with the business account 

• Next sign out of any personal Microsoft account in Office, Windows account settings, and browsers.  
• When prompted with “Which account do you want to use?”, select Work or school account and complete the organizational sign in.  
• To avoid the account selection prompt in the future, rename the personal Microsoft account so it no longer uses the company email as an alias by adding a new alias, making it primary, and removing the company email from the personal profile.  
• In addition, if the custom domain still triggers the mixed‑identity prompt, try signing in with the tenant’s default sign‑in name format, for example ******@yourcompany.onmicrosoft.com, which cleanly targets the organizational identity for your tenant. 

I hope this response has helped address your question and clarify the behavior you're experiencing. Please feel free to reply if you have any further questions, I would be happy to assist further.  

Thank you for your patience and your understanding. I look forward to continuing the conversation.  

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Answer 2

The email address is currently associated with both a personal Microsoft account and a work/school (business) account, and Office on the devices is trying to use the personal account, which is not valid for the Microsoft 365 business subscription.

Use these steps to correct it:

1. Sign out/remove the personal account on the affected PCs
   On each user’s PC:
   • In any Office app (Outlook, Word, etc.), go to File > Account and sign out of all accounts shown there. Close all Office apps.
   • In Windows Settings > Accounts > Email & accounts and Access work or school, remove any entry that uses the personal Microsoft account for this email address.
2. Ensure the work/school account has the license
   In the Microsoft 365 admin center (admin only):
   1. Go to Users > Active users.
   2. Select each affected user.
   3. Open Licenses and Apps.
   4. Under Licenses, make sure the correct Microsoft 365 Business license is checked. If it is already checked, uncheck it, Save changes, then check it again and Save changes to refresh the assignment.
3. Sign back in with the work/school account only
   On each PC, open an Office app (e.g., Outlook):
   • When prompted to sign in, enter the same email address.
   • On the “Which account do you want to use?” prompt, choose the Work or school account / IT group option, not the personal account.
   • Complete sign-in and activation.
4. If the “Which account” prompt keeps causing confusion
   Because the same email is used for both a personal and a work/school account, the prompt will continue to appear. To avoid this long term, rename the personal Microsoft account so it no longer uses the company email:
   • Go to the Manage how you sign in section of the personal Microsoft account.
   • Add a new alias (for example, an Outlook.com address) or use an existing personal email, then select Make primary for that alias.
   • After that, the company email will be used only for the work/school account, and the “Which account” prompt will stop.

If any user still cannot activate Office after these steps, run the Microsoft 365 sign-in troubleshooter mentioned in the context or follow the additional activation troubleshooting steps.

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References:

• Which account do you want to use?
• What’s the difference between a Microsoft account and a work or school account?
• Microsoft 365 apps activation error "Another account from your organization is already signed in on this computer"
• Change account settings in Microsoft 365 for business