Nothing happens on Login process after entering the password

[MurzNN]

I've started the app, unlocked it using pin, filled my Email, pressed Login button, entered my password, the password entering window disappears, and then - nothing happens even after several minutes:

The installed version is 0.2.15 from Flatpak. By the way, how to get the exact currently running version number from the app directly? Running something like flatpak run com.quexten.Goldwarden --version doesn't work.

What can cause this issue, and how to fix or debug it?