I have exactly the same issue after having to do an internet “Restore” of my HD on my mac mini.
I have sent a support request, but Steinberg’s response time is the worst I have ever come across from any software company since Yamaha took them over. The last two times I sent a support request, they took over a week to reply…totally unacceptable for a professional musician / composer who has deadlines.
Anyway …I have tried all the recommended fixes such as re-installing the eLicense control center and doing maintenance, deleting my Cubase 6 prefs folder from user/library/Preferences.
So if anyone on this forum has a fix, please let me know.
so far non of the fixes I’ve seen here have worked.
So it looks like I might have to back up all my files and do a total wipe of my HD, re-install OSX and then all my apps, plug-ins etc 