Register the new Teams as the chat app for Microsoft 365(requires restarting Microsoft 365 applications) is not working

Thanks Thomas. Our GPO team initially told that there is no GPO deployed for same. After investigating myself we found that there is a GPO policy pushing classic Teams "Teams" as DefaultIMApp.
Disabled the GPO and this resolved the issue.

Others you can run below command to get the client machine's applied GPO list and find the culprit policy.

cmd:\> gpresult /h c:\temp\gpresult.html

We found the issue internally to be a old policy that was writing "Teams" to the DefaultIMApp registry at a periodic check-in, that's why it was happening. New Teams is supposed to contain the value "MSTeams". Running Procmon on that registry path helped determined that.

My company also has the same issue. The checkbox for "Register the new Teams as the chat app for Microsoft 365", keeps getting unchecked automatically in new Teams client.

Users have to check if again and restart new Teams & Outlook classic client.

We have opened a ticket with Microsoft for this. This issue is still unresolved for now.

MS Teams not showing in both the registry location. Please help.

Thank you so much for this, It works!

I have had the original issue with the checkbox not clicking in Teams and running as administrator fixed it,

however, after restarting Teams and Outlook I still did not see the presence status in outlook.

After updating the Reg keys you listed it worked after restarting the apps.

Many thanks!!!!