This worked for me:
Settings → Personal → Security → “Create new app password” → Copy the credentials and use them within the iOS.
It seems when you connect to the cloud not from web browser you need to set “app password” in order to connect. I did the same when for the Ubuntu online accounts as initially did not work with my regular password.
i still bave the same problem. I can setup the caldav account link in the iPad settings succesfully, but the Calendar does not sync.
error on ipad calendar “unable to update calendars”
i am using https://myServerurl/remote.php/dav/
and iOS 17.1.1
any ideas?