After a phone repair, I had to sign in to my Firefox account. It wanted my 2FA code but these had gone from my Google Authenticator app. So I witched of Firefox 2FA on my computer, and signed into my Firefox account on my phone. Then I wanted to re-enable 2FA. But after scanning the QR code in the authenticator app, the Firefox 2FA screen would not accept the code generated by the app. I have tried this with Google Authenticator and Authy. Same problem.