Adding New User to Cloud Support Portal

Can anyone guide me to how we're supposed to provide new users access to the Cloud Support Portal?

If a new user to our company registers an account within MOS, the only option to request access uses CSI number which grants access to the old support site.

If I manually go into Administration on the new Cloud Portal, click Add Users to User Groups, and select any Tenancy, that new user does not exist to select. I guess my question is how do I get a new user to display in the list to grant access on the Add User to UserGroup screen?