A Microsoft file hosting and synchronization service.
Exact same thing on our end. It started around 2-3 weeks ago. I thought it was related to recent OneDrive for business sharing folder advisory. BUT I'm glad I saw this post.
Generally, it happens randomly on users' PC. But it starts to happen way more often. Sometime closing out OneDrive, deleting temp files, reboot, and manually click to sign in to OneDrive (no prompt for password , just goes in) will work. But a lot of times it still doesn't login. Occasionally instead of that error user gets a login prompt for password. After entering password and confirming MFA, it gives error messages as if some Conditional Access rule was causing it. This whole issue usually gets resolved on its own within 24-48 hours. And I'd know by either rebooting the PC or opening OneDrive and clicking 'sign in' and it just goes in.
I just had one user happen to him 2 days in a row.