I am having the same problem here since the last update of Enpass through the Microsoft Store (6.42.662.0) on my Windows 10, using Firefox .
After the update, Enpass acted as it was a first install, displaying its "Welcome" screen, and asking me if I want to restore a previous vault. When I try to restore my Vault on Google Drive, it opens a Google connection page to allow Enpass access my account, and when I allow it, Enpass crashes. If I restart Enpass, I'm back to square one.
Enpass still works fine on my iOS 13.5 iPhone, and an older version of Enpass (6.4.1 (642)) on another computer running Windows 10 works as well.
I tried uninstalling and reinstalling Enpass, but with no effect (I didn't found any Enpass folder in my AppData hidden folder).
Thanks for your help ! I can send you any more details or logs you might request.