This error is the result of a licensing issue with PPM itself.
The PPMLOC.INI file contains a user ID which is the culprit.
This file doesn’t get stamped by RProDB or even the PPMSRVR.EXE, but by Workstation PReferences.
Solution: Go into Workstation Preferences on WS with a valid, allocated license and then save the preferences to stamp the PPMLOC.INII file.
You can delete the file then restart rpro, go to ws preferences & save