Once you setup the Virtual Appliance, you will be asked for credentials to access the dashboard.
If you enter your Management Portal credentials, these will not be accepted and you will receive a message in red "credentials for user [your email] are invalid".
When you login for the first time, the credentials that you are being asked for are pertinent to the built-in admin account of PMC.
These credentials are rather given to you per the document
PMC Setup Guide:
"The built-in PMC user account with administrative privileges is ‘pmcadmin’. The password is ‘pmcadmin’ too".
Once you enter the right credentials and have full access to the dashboard, then, you can proceed to create users and credentials for access to PMC.
REV 03.20