We had a guest added to our teams account who encountered a quite strange behaviour when logging in without access to any vault. The desktop app just redirected back to the login page showing an error which didn't make much sense. It took us a while to figure out that this was caused by the guest user not having access to any vault. After giving the user access to a vault the app functioned normally.
Would be great to show a screen prompting the user to request access to a vault or similar. I'm guessing you are probably already aware of this, but wanted to let you know just in case.
1Password Version: 6.4.377d
Extension Version: Not Provided
OS Version: Windows 10
Sync Type: Not Provided