Robinair A/C machine won't work

[gearheads78]

Anyone know about these machines? Just bought a used (barley) Robinair 17800B recovery / recycle machine for my home shop. It was bought from a closed down shop at auction so I am stuck with it so I need to get it working.

All of the fuctions start but does not matter if I am trying to recover, recycle, fill the unit from a fresh tank of 134 I get a HI-P (High Pressure) message and the function stops. Ive checked all the trouble shooting in the manual and talked to tech support at Robinair (They were no help other than offering a number to a repair man)

Ive hoping this is a common issue someone can give some pointers on. It looks near brand new and the run meter only shows 5 lbs of refrigerent has gone though the filter.

thanks in advance