There is currently a bug where it will say "connection error" even if there is a 2fa auth issue. Fix deploying rn. Can you login directly to your instance? If so, can you try again?
Just to add that 2FA does not work reliably on Lemmy instances running less than 0.19. (It’s possible to get locked out) It’s generally recommended not to use it unless your instance has upgraded.
As I say I’m talking generally, not about your Voyager problem.
It’s not that you can’t log in at all, it’s unreliable. You can get into a state where authentication doesn’t work and there’s not much an admin can do. Check on the Lemmy dev community for some more detail.
0.19 is not far away and some instances are already running the release candidate.