If you create a template on the core server (even a blank template that just has, for example, a wait command) and then add that device to it and try to start does it:
A) Stay in Pending forever
B) Switch to Active for just a few moments, then go to Pending\Delayed and stay there forever
C) Run just fine
D) Something else
Let me know.
Thanks for your response. The issue has now been resolved after a number of server restarts all but one PC started provsioning. Support recomended I "check the IIS worker process is set to recycle every 120 minutes rather than the default value". This seemed to fix the last PC that had a problem.