solenoid

I have a question regarding my regulator solenoid. I bought a used Milwaukee regulator and have hooked it up to a 5 lb co2 system. Everything is great except that the solenoid is not working. I can only assume it's stuck in the open position as the reg is working. When I plug it in or unplug it...

For sale is brand new never used equipment : - Aluminum CO2 Cylinder - 5 Pound, manufactured by Catalina Cylinders in Dec 2011, hydrotest good till Dec 2016 - $80 - Milwaukee Co2 MA957 Regulator Set - dual gauges, flow regulator, needle valve, electronic solenoid and bubble counter - $100