I am a microsoft partner, a customer is experiencing a Tenant lockout and trying to help him regain access

A customer for which we are the reseller and partner has lost access to the sole account with Global Admin rights in his tenants.

When they sign in with the admin account, after entering the password, the MFA says it will send an SMS message to their phone, but an error message in red reads "your account is not verified". No message is sent, and no other button but "cancel" is visible.

The details display an error code 399287.

We used to have a DAP relationship, but with the switch to GDAP this was not renewed, so we cannot directly do anything on their tenant to assist or reset the MFA.

We have created a support ticket (in our tenant), that reads it is going to be routed to the Data Protection team, but it's been a week without any further updates in the ticket.

I am wondering what is the correct way to create this support request (if I made a mistake) or the correct way to escalate the ticket (if possible) .