How to restore access to Microsoft Partner Center

Question

Hey, we cannot access our Microsoft Partner Center account since the person who set the account up left the company, leaving invalid credentials which doesn't allow to log in successfully. We tried to search through the ways to restore an access listed on this page:
https://learn.microsoft.com/en-us/partner-center/support/schedule-support-appointment#account-access-problems
and contacted the support mentioned in there, but we got redirected to this community in order to get a response. We'd be glad for any tips on how to proceed