I have the Praxair Platinum 4323391-75-000. It's a dual stage SS regulator.
nice regulator you have there, it is a top CONCOA.
give it a simple leak check.
1. put the system on co2 tank, charge it with co2.
2. set the output pressure to 50 psi, then solenoid off, co2 tank valve close.
3. leave it for 6 hours, if nothing change, means no leak from the CGA320 connection to the solenoid(not cover the parts or the tubing after the solenoid).
4. the parts/tubing connections after the solenoid, use soapy water to check leak.
if no leak, one or two psi rise after solenoid power off, may be the problem of a lazy stainless steel diaphragm, should be ok if you set the output pressure high enough, about 40-50psi.