I just had some struggles logging into my account. I got in on Firefox Desktop and Jerboa after a password reset, but I still can't log in on Firefox for Android. When I try to log in, it says "logged in" in a small popup, but it's not logged in.
It's not that big of a problem for me, but I can imagine if someone has that problem without using an app it could get annoying.
I'm having the same problem. I've cleared cookies and sometimes can log in if I disable tracking protections, but then get logged out again. I can log in fine on Firefox on desktop.