When I open the Teams app on my machine (Windows 8.1), I get a blank login window. I've tried completely uninstalling it and reinstalling it and the problem remains. My company's IT people can't figure it out either. The only way I can get it working is to close the blank login window, then it reappears, then I close it again and it says "Modern authentication failed here. Status code 4c7". Then it logs in some other way and works.
How do I fix this?74 votes
This is expected behavior when an organization’s SSO doesn’t have Modern Auth enabled correctly with fallback auth. For more details around the 4c7 error and sign-in issues, please see the following articles:
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