[Mark McLeod]

The working pressure side, where the solenoid valves are, must be 60 psi or less.
The high pressure side, where the compressor is, should be at 115 to 120 psi.

If your high pressure side cannot get above 80 psi, then the high pressure regulator might be plumbed incorrectly.
On the regulator look for an arrow. The tail of the arrow points to the only port that can be high pressure.
If any other port gets the high pressure line, the regulator won't allow pressure to go above whatever it is set for.

Another less-likely possibility is that the pressure safety valve is way off and needs to be adjusted.