Two-Factor authentication (2FA) works with a 6-digit time-based code (TOTP:Time-based One-Time Password) that is valid only for thirty seconds, so make sure that time and timezone are correct on all devices especially on the mobile device with the Authenticator App that generates the TOTP code. More info: *https://support.mozilla.org/en-US/kb/secure-firefox-account-two-step-authentication *https://support.mozilla.org/en-US/kb/what-if-im-locked-out-two-step-authentication