Hi @tobihagemann
This seems to be back with Version 2.2.5 (949) and onedrive.
I had to change my onedrive credentials due to a mail address change.
So I deleted the onedrive connection, and set it up again.
Login etc works like a charm., but when the authentication process is finished, the above error message appears. Same when I try to add/create vaults and select the onedrive connection.
I am not getting to the point where i actually can select a vault.
I’ll send you a log file.
Edit:
I tested with testflight version: same result.
I deleted the app and did a new install. googledrive, webdav works fine, onedrive still the same behavior (didnt test other connections). so actually I have no idea how to access my onedrive vaults with the iOS app 
Edit2: just tried the same thing on the iPad. No issues at all, everything works. I have no idea what could be the difference to the iPhone.
Edit3: deleted the connection on iPhone again, and added it again. (Which is exactly what I did before today a couple of days). Now everything works there as well. Still no clue what’s going on, but we’ll… as Long as it works now 