Precondition: This page relies on an existing Runbook procedure to be in place. Read: How to deploy Microsoft Runbook.
The following procedure requires tenant administrator rights, including access to the mailbox.
Whenever a service has been updated in the Service Settings, a "Trigger Runbook" link is starting the deployed procedure.
Note that any Microsoft Teams "team owner" can trigger this process.
The Runbook process will send an Email to an Azure Resource Group called "Approvers" - see How to deploy Microsoft Runbook. Any member of that group can give consent to this change.
Please note that the approval Email can take a few minutes to reach the administrator group.
Reload Settings Page and Check
Check back into the affected Service Settings. When the runbook procedure was successful, the settings should be updated and the warnings are removed.
To test if the UPN is working correctly, a "Test Call" is recommended.