So with the door open the corner valves will not operate, but the pump should run. At the same time as the pump runs the Diaphragm Solenoid Valve should open to force air into the tank. This is easy to check.
Also did you check the dryer is ok ? You can unscrew the top and check if the desiccant is ok or not.
- Remove exhaust filter & the air-line that feeds tank.
- When the pump runs, check for air coming out of either tank feed, or exhaust port.
- If there's air coming from exhaust port, then diaphragm valve or solenoid isn't working correctly.
- If there's only air coming from tank port, then 1st measure pressure, and 2nd wait for tank to fill.
All he needs to do is follow the instructions in the "How to".