After installing May 11 Update KB5003169 for Windows 10 1909, some users experience problems logging into Microsoft 365 desktop client apps such as Microsoft Teams, OneDrive for Business, and Microsoft Outlook.

Microsoft is aware of this problem and is working on a resolution for the issue.

Microsoft: After installing this update and restarting your device, you might be unable to sign in to some Microsoft 365 desktop client apps such as Microsoft Teams, OneDrive for Business, and Microsoft Outlook. You might also receive an 80080300 error or “We ran into a problem. Reconnecting‚Ķ” when attempting to authenticate or sign in to Teams.

Note Mobile, web, and non-Windows versions are not impacted.

To mitigate this issue on most devices, you can restart your device a second time. Most devices will sign in to affected apps as expected for all subsequent restarts after the first restart that completes the installation of the update. If restarting does not mitigate the issue on your device, you can use the web versions of the apps:

Source: Microsoft