Logging in to my new account leads to error

I can’t login through the website or the app. The website returns this error message: “Server Error: /auth/bnet/callback”. The app tells me “login session expired”. But my old account works just fine on both the website and the battle net app. I confirmed that the new account exists by reseting its password, but I still can’t use it. This seems to be a server problem, and I can’t fix it as a user.