If you are getting prompted for a six-digit code when you sign in but lost access to your authenticator app, please use one of your backup codes (downloaded when you enabled your authentication).
Braintrust users can download your 2FA recovery codes from the settings menu: https://app.usebraintrust.com/settings/privacy_security/
This will provide the ability to log back into your account if you get a new phone or delete the app.
If you did not save your backup codes, email support@usebraintrust.com to disable your 2FA from the back end.