> But you have setup SMS 2FA enabled
No. I did not. Nor do I now.
I had a TOTP setup in 1Password and Mongo was telling me MFA _wasn't_ set up and sending me through the MFA setup flow again.
All options, SMS included, were failing in that MFA setup flow they pushed me in to.
They're back now and my existing TOTP token is generating one time use passwords that work now.