Account recovery
Forgotten passwords, lost authenticators, and the order the two have to be done in.
Three things can lock you out, and they have different answers. Doing them in the wrong order is the usual reason somebody gets stuck.
The account was never confirmed
Symptom: signing up says the address is already registered, and signing in says the account is not confirmed. Go to Confirm your account and request a new code.
A forgotten password
Use the forgotten password link on the sign-in screen. A code is sent to your confirmed address.
A lost authenticator
Ask us using Contact us at the bottom of any page. A member of staff clears the enrolment after checking the request is genuinely from you, and your next sign-in enrols a new one. The reset is recorded with the reason.