Apple Business Manager - How Do You Change an Admin username/password if you get locked?

How does a company get access back to the Apple Business Manager portal if they have lost access? Our prior Apple Business Manager admin left the company and did not provide any credentials to the Apple Business Manager portal and had not assigned any additional managers to the portal prior to leaving the company (I am now in charge of ABM as a new hire). As a result we are locked out of our Apple Business Manager portal and need to reset the username and password to get a new admin assigned and assign new managers as well.