If you have lost your MFA method, please reach out to the Support Team by opening a Support Chat. You can do this clicking the green chat bubble in the bottom-right corner of the MongoDB login page:
Please note that Atlas Basic chat support is generally available Mon - Fri during business hours.
Upon successful login, if you intend to re-enable Multi-factor authentication, we highly recommend configuring at least two MFA factors (as noted in our documentation). This avoids future lockout situations as you can still access your account if one MFA factor is unavailable.