We need a few details to see where the login gets stuck:
Please send a screenshot of the screen or error message you see when you try to sign in.
Please tell us which device you are signing in on (Windows, Mac, iPhone, Android) and where Roon Server runs (Nucleus, ROCK, PC, NAS).
Please tell us what happens after you enter your email and password, for example whether it loads without end, shows an error, or returns to the sign-in screen.
Please tell us whether the VPN on your router is turned on, and whether signing in works with it turned off.