The timing doesn’t fit perfectly. The Dec 4 report linked from here saw a Nov 30 certificate, still in use now, which seems like it should have caused the TrustFailure problem on your Dec 9 backup. So that’s strange.
Ignoring that, your new 401 - unauthorized isn’t being reported elsewhere that I’ve seen, so might be some configuration (or was there a configuration change?) on your system. Backblaze themselves have posted Quickstart Guide for Duplicati and Backblaze B2 Cloud Storage which unfortunately doesn’t say precisely what to put where, but at least indicates they might be willing to take a followup support question if needed.
You could test some other Backblaze B2 client to see whether you can get it authenticated, and you could look more closely at your Duplicati setting using Export As Command-line which will make it clearer which field is which, spot inadvertent characters, etc. Mine contains “auth-password=K” … Does a K mean key?