How to fix issue: "I don't even input a letter, it shows "Sign in failed" error message?"

When you meet this issue, you can check if the app: Microsoft Authenticator is installed on your phone and you have signed it with your Microsoft account. If it does, please try to fix this by following way:

1. Long press the app:  Microsoft Authenticator and go to the app info page.
2. Click: Force stop option

After 10 minutes, if this issue still can't be fixed, please feel free to send a feedback to us.

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