Hi,
We have found that if you don't update the Creo 2 "Addons" (Creo Platform & Creo Thumbnail Viewer) - found in the addons folder of the Creo loadpoint, then the server registration can get dropped for some strange reason.
Ensure that you are running the correct versions of the above to suit the exact maintenance release of Creo 2 that you are runing, by manually running the installers in the addons folder.
That might be your problem.
Rgds
Gary