Error in switching from classic to new outlook in 365

Question

I am asked to login i get thois error

{"SessionId":"Moderator note: personal info removed","Timestamp":1772564924009,"Error":"INTERACTIONREQUIRED"}

Answer 1

Dear @Virginio Chiodini,

Thank you for reaching out to the Microsoft Q&A forum. I understand how frustrating it is to encounter an error when trying to switch to the New Outlook. 

The error code "INTERACTIONREQUIRED" typically indicates that the authentication process stalled because the system required you to perform a specific action, such as re-entering your password, completing a Multi-Factor Authentication (MFA) challenge, or accepting new terms of service, which the automatic transition process couldn't trigger automatically. Additionally, the errors INVALIDCREDENTIALS and INTERACTIONREQUIRED may indicate that the application is requesting modern browser-based consent (OAuth) or an application-specific password, but the account is configured with generic POP/IMAP using Basic authentication.

I recommend following these steps to refresh your login state and clear the error: 

Step 1: Sign Out and Sign In via Web: 

• Open your browser and go to Outlook Log In | Microsoft 365 
• Sign out of all accounts, then sign back in. If there is a pending MFA request or a password update required, it will prompt you here. 

Step 2: Clear the Outlook Cache: 

Always close Outlook completely (and any other Office apps) before touching the folders below. 

Prefer to rename over deletion on first attempt renaming preserves a backup copy you can restore quickly. 

If you rely on locally stored PST files or other non-cloud storage, verify where those files live; the steps below do not target PST/OST files inside your Documents by default, but caution is still advised. 

• Close Outlook and any Office apps. 
• Press Windows Key + R to open the Run dialog. 
• Type %localappdata%\Microsoft and press Enter. 
• Locate the folders named Olk and OneAuth. 
• Right-click each folder and choose Rename. Add “.bak” to the end (for example, Olk.bak and OneAuth.bak). Alternatively, copy the folders to a backup location before deleting. 
• Start Outlook normally. 

Step 3: Check for Account Conflicts: 

• Go to Windows Settings > Accounts > Access work or school. 
• If your account is listed there, select it and click Disconnect (if it's a work account) and then Connect again to refresh the token. 

Step 4: Repair the Outlook App: 

• Go to Settings > Apps > Installed Apps. 
• Search for Outlook (new), click the three dots, select Advanced options, and click Repair or Reset. 

According to Microsoft documentation on authentication errors, "Interaction Required" occurs when a silent token request fails. Manually signing into the web version usually satisfies the "interaction" the app is looking for. 

Microsoft recently announced the Exchange Online capability to use OAuth authentication for POP and IMAP and SMTP protocols. Also, tenants are encouraged to disable Basic authentication, and move to a Modern authentication tenant for modern clients. 

If your mail provider only offers Basic auth (username/password) with no app‑password mechanism or OAuth, and you're trying to configure an Outlook profile by using POP and SMTP or IMAP and SMTP, you'll notice that Outlook doesn't connect or authenticate. The reason is that Outlook supports Modern authentication only for Exchange profiles, Outlook.com, and Gmail at this time. It's also documented in Deprecation of Basic Authentication in Exchange Online. 

For more information, please refer to Microsoft Official Document here: Can't connect to Outlook by using POP/IMAP and Modern authentication 

If the provider has only Basic auth and no app passwords or OAuth, New Outlook will likely not connect. I recommend you use the provider’s own app or webmail while they modernize auth. Then, keep that account in classic Outlook as a stopgap only if the provider still permits Basic auth (be aware this may stop working as policies tighten) 

I completely understand how critical this feature is for users who rely on external accounts. This is a significant gap, and your feedback can help influence future improvements. Therefore, I highly recommend submitting your feedback directly to Microsoft Ideas · Community, where our product development team can know your requirements and ideas for product improvements. If enough users raise ticket for the same idea, Microsoft may consider adding this feature in the future.  

Note: As Microsoft Community moderators, please note that we are not involved in product design decisions and do not have direct access to the development roadmap, we want to assure you that your feedback has been acknowledged and is valued.   

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this. 

Please understand that our initial response does not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution. 

Thank you for your patience and your understanding. If you have any questions, please feel free to reach out. 

I'm looking forward for your reply. 

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Answer 2

Delete the local new Outlook authentication/cache data, then start new Outlook again so it can prompt for fresh sign-in and consent.

1. Close all Microsoft apps (new Outlook, classic Outlook, Teams, etc.).
2. Open File Explorer and in the address bar enter %LOCALAPPDATA%.
3. Go to Microsoft and delete these folders if they exist:
   • Olk
   • OneAuth
4. Restart Windows.
5. Launch new Outlook again and sign in when prompted.

These folders are recreated automatically and clearing them often resolves sign-in and token issues such as INTERACTIONREQUIRED when switching from classic to new Outlook.

If new Outlook still fails to start correctly after this, run olk.exe --clearLocalState from Run (Win+R) and then open new Outlook again to reconfigure the account.

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References:

• Detected a problem launching new Outlook - Microsoft Q&A
• New Outlook has stopped working, Fails when starting after 30 to 60 seconds - Microsoft Q&A