I was getting no errors in my Active Directory Sync and only when I turned on Verbose logging I got the following in my ULS logs.

PS: NoError (0) The Active Directory Group being synchronized with contains no members.

When I typed in my group name all groups appeared as “DOMAIN\my group name” except for a few which appeared without the domain name. These ones synchronized without any problems.

It looks like the way these groups were created e.g. “DOMAIN\Domain Users” were created without a display name and Project Server seems to not be able to synchronize the users within the group and report and empty group.