From bleepingcomputer.com
Microsoft has fixed a known issue causing Microsoft 365 to experience authentication issues when logging into desktop client apps like Microsoft Teams, OneDrive for Business, and Microsoft Outlook.
When attempting to sign in, users are shown a message saying, “We ran into a problem. Reconnecting…” and asking them to restart the application.
This same screen will also display 80080300 error codes at the bottom left of the window and suggesting reaching out to an IT admin if the login problems persist.