Microsoft confirms and fixes the Outlook login error [4usqa], CAA2000B and 49dvs

[German]Microsoft is not having a good run with its Outlook Classic for Windows and Mac at the moment. The company has just had to confirm logon errors that are being reported with the error code [4usqa] (or CAA2000B and 49dvs).

Outlook classic error [4usqa]

I had reported on May 13, 2025 in the blog post Outlook fails with error [4usqa] since May 2025 about problems with Microsoft Outlook (Classic). Blog readers had informed me that since around May 5, 2025, the Outlook login has failed with the error code [4usqa].

Those affected receive an error dialog with the content "Error Something did not work. [4usqa]" is displayed. The error dialog states that the affected person should contact the administrator.

In the blog post, the assumption was made that it had to do with the Skype shutdown on May 5, 2025. In the text, I described various workarounds that blog readers have used to solve the problem (at least temporarily). Some of the workarounds also work for the sign-in error CAA2000B, as can be read on the linked websites.

Microsoft confirms Outlook error

neowin.net noticed that Microsoft published the support article Errors CAA2000B, 4usqa, and 49dvs when trying to sign in to classic Outlook and Outlook for Mac on May 14, 2025. The support article states that since May 7, 2025, some users have received the login error described above when starting the classic Outlook "Error Something didn't work. [4usqa]" as described above. Outlook informs that the user could not be logged in. If this error persists, those affected should contact the system administrator and enter the error code CAA2000B.

Microsoft says, initial support cases indicate that the problem was caused by a deactivated service principal for the resource ID: 40775b29-2688-46b6-a3b5-b256bd04df9f. What Microsoft expresses somewhat cryptically, I had clearly stated in the blog post above. Blog reader Bastian R. had told me that Microsoft had probably tinkered with something and deactivated the "Microsoft Information Protection API" in the tenants. He referred me to the reddit.com thread PSA: error CAA2000B when signing into Outlook, where someone issues a corresponding warning.

The administrator must reactivate this deactivated API. The reader wrote: "If you reactivate the app in the Entra portal, Outlook works again immediately." Microsoft also described the outlined way to fix the problem in its support post. However, the feedback from blog readers was that the API was sporadically deactivated again for individual accounts.

This problem should no longer occur since May 14, 2025. Microsoft writes in its post that this problem was resolved by a change to the service on May 14, 2025. It states that users should restart Outlook to apply the change. Further details can be found in the incident in the Microsoft 365 Service Health Dashboard at EX1072812.