Can you login to the Firefox account via this web page?

• https://accounts.firefox.com/signin
• https://accounts.firefox.com/settings

Thanks for replying! Unfortunately no, I get the same error message.

I've got the same problem in Firefox (even in safe mode), but I can login using Chromium.

I did switch my primary email address some time ago, but I'm getting the error for both my old and new primary email address. This is especially strange since I completely removed my old email address, so it shouldn't even be associated with my account any more. When I did login through Chromium I at first got the error message "This account is not active. If you believe this to be an error, please contact an administrator" (not verbatim). I just tried a second time however and it worked.

I've previously had another problem logging in using Firefox, where it prompted me to type in an email verification code, although I had 2FA with an app enabled. I didn't get any emails, but wasn't prompted for my actual 2FA code either. Again, using Chromium I was correctly prompted for my 2FA code and was able to login. When I tried again about a month later, logging in using Firefox did work again. Not sure if that could be related.

Edit: I just had a look at the difference between the requests in Firefox and Chromium and it looks like for some reason Firefox is sending the parameter 'verificationMethod: "email-otp"', while it's "verificationMethod: "totp-2fa"' in Chromium. I have 2FA with an app enabled, so it makes sense that only the latter would work. Firefox also sends 'originalLoginEmail: "my.old.primary@email.com"'.

So I went into the developer tools and removed all the cache/local/session storage and now everything works fine. It seems the problem is that changes to your account like enabling 2FA or changing your primary email address are not reflected in Firefox' local storage, leading to it making requests using parameters containing the wrong email address or authentication method.