locked out of 365 admin portal and cannot verify MFA

we are a small business with an admin account that was linked to my bosses phone. when signing in online he was asked to verify via the authenticator app, but no code was showing and no 6 digit code was displayed in the app so he removed the account from his app and when trying to put it back on, he cannot add the account back without verification so it just goes round in circles.

We cannot log into the aka.ms site without verification and seem to now be indefinitely locked out of the account so we cannot get into the admin portal since no other verification methods were set up at the time of creation other than to the app on his phone..

I think the account may have been blocked for suspicious activity but there is no way to confirm this since we are both locked out of the account due to the above issues.

We need to get back into this account urgently for the purpose of the business, how can we verify the account with Microsoft?