Hi, I'm John! I will help you with this.
To help narrow down the issue:
- Which application is not opening when you try to sign in with Microsoft Authenticator?
- Is it Outlook, Teams, OneDrive, Microsoft 365, or something else?
- Also, are you getting any error message, or does it just fail to log in?
Click "Add comment" to let me know.
Regards,
John J.D.