Locked out: 2FA enabled on my account but I haven't set it up

I have a Firefox account since long, I use it to publish my add-on. I haven’t signed in recently and didn’t take action when I’ve received an email that developers should move to 2FA. Now I’m trying to sign in to my account but it’s always asking for the 6 digits security code, even though I have never set up 2FA on my account and thus don’t know which authenticator app I need to use. Neither do I have recovery codes - naturally. Can anyone help me with my account?
Best regards,