Try unscrewing the check-valve from the valve/regulator, so your filler system is just dumping to the room. Open the source-tank valve, then open your solenoid. If there is a small but inadequate flow coming out the check valve, you will know.
Again, if it all works properly without the solenoid, but not with the solenoid, perhaps the problem is the solenoid?
I don't know who peter paul is, so I have no information to convince me the solenoid is working properly at 200+ atm.
ADDED:
Actually, regarding the first paragraph, I'd open the solenoid first, then crack open the source-tank valve. It should be a straight-through high-pressure flow. Then do the same thing without the solenoid.