MicrosoftMartin Holderegger : We are having this issue all the time when setting up MTRs. The following trick often solves it (even though we don't understand the underlying root cause): we have configured WiFi and LAN on the MTR. When the sign-in issue occurs, we simply pull the LAN wire, the device falls back to WiFi and the sign-in issue disappears immediately. Plug LAN back in and you are good to go.
There can be many reasons why the sign-in fails, but in cases where we can rule out network and account issues for sure, this approach helped big time.
