It seems like I’m not able to log in to Eternity with my account from the lemm.ee instance? I have been able to sign in with a lenmy.world account. I’m posting this from the Voyager app where I had no issue signing in.
Try changing to anonymous (same menu where you add an account) and them try to login again.
I had the same problem, and there is a bug that if you try to login while using another account it results in a login error.