CO2 gauge problem

[BC Mosaic]

It seemed like the needle valve on my CO2 gauge was sticking and so I soaked it overnight in vinegar. This morning it was nice and bright and freewheeling. I reassembled the unit and fired up the system (calcium reactor)and it seemed to again not produce a steady controlled bubble stream. The CO2 tank is not empty. Is it my solenoid then that is faulty? How do I check? Either item is pricey.
Thanks