After a recent tenant-to-tenant migration iPhone users were unable to connect to Outlook or Teams on their phones. After entering their credentials they would be connected to the old tenant which now contained “onmicrosoft” in the domain name. The solution was to use Edge to clear the sign-in cache.
Clearing Microsoft 365 sign-in cache via Edge.
- Down and run Microsoft Edge for the iOS app store.
- Type edge://signin-internals into the address bar and press go
- Click “Remove all accounts” option on the page
- Close Edge and restart the Microsoft 365 sign-in process