Error code [4usqa] when logging into MS Outlook desktop version. It's not linking to OneDrive files.

Question

For the past month I have received this error. I have not been able to resolve by updating Outlook or other recommendations.

Answer 1

Hi DonsterG,

Welcome to Microsoft Q&A.

For classic Outlook for Windows, Microsoft documented that many [4usqa] sign‑in errors that started around May 7, 2025 were caused by a backend service configuration issue (a disabled service principal for the Microsoft Information Protection API).

Microsoft implemented a service‑side fix on May 14, 2025, so for most users, fully closing and restarting Outlook is enough to pick up the change.

For reference: Errors CAA2000B, 4usqa, and 49dvs when trying to sign in to classic Outlook and Outlook for Mac

What to try (home users):

• Fully close Outlook (right‑click Outlook in the taskbar > Close, and if needed end OUTLOOK.EXE in Task Manager), then restart Outlook.
• Make sure Windows and Office are fully updated, then reboot once.
• If it’s still happening after multiple restarts, local sign‑in data can sometimes contribute. Try clearing saved Office/OneDrive credentials in Credential Manager, then sign in again.

If you’re using a work or school mailbox: The same article also lists an admin‑side resolution (re‑enabling sign‑in for the Microsoft Information Protection API in Microsoft Entra), which requires an IT administrator.

If you can paste the exact last line of the error dialog (in quotes) and confirm whether this is a home or work/school account, I can point you to the most appropriate next step.

Please let me know if this proves useful to you, or if you would like further assistance.

I'm looking forward to your reply.

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Answer 2

Error code [4usqa] when signing into classic Outlook is associated with sign-in failures caused by a disabled Microsoft Information Protection API service principal. This can also prevent access to OneDrive/SharePoint-based modern attachments.

To resolve the issue:

1. In a browser, go to the Entra admin portal: Microsoft Entra.
2. In the search box, search for either:
   • "Information Protection", or
   • The app ID 40775b29-2688-46b6-a3b5-b256bd04df9f.
3. In the search results, select Microsoft Information Protection API.
4. On the Microsoft Information Protection API page, set Enabled for users to sign-in to Yes.
5. Select Save.
6. Restart classic Outlook and sign in again, then test attaching or opening OneDrive/SharePoint files.

Note: This change requires appropriate admin permissions in Microsoft Entra. If not an admin, contact the Microsoft 365/Entra administrator and provide the error code [4usqa] and the guidance above.

Additionally, Microsoft has already deployed a service-side fix for this issue (referenced as incident EX1072812 in the Microsoft 365 Service Health Dashboard). After enabling the Microsoft Information Protection API and restarting Outlook, the sign-in and OneDrive attachment behavior should return to normal.

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References:

• Errors CAA2000B, 4usqa, and 49dvs when trying to sign in to classic Outlook and Outlook for Mac