Moroso oil accumlulator problem

I emailed the Moroso tech dept but they have not answered.

I'll give the short story first. I installed the 1.5 qt size one earlier this year and it worked great. (Fiat Abarth 850TC vintage racer, 1050cc)

I use it on a street car with remote oil filter and cooler to prepressurize the system, and the last time I started the car it had been sitting for about 2 mos. I normally pressurize to about 45psi, and when I opened the manual valve the gauge only dropped to about 25 psi and stopped decreasing. I started the car but the system had not been prepressurized very well.

Today, 2 weeks later, I opened the valve and the gauge stayed at 45 psi and did not move at all.

Is the piston stuck? Do I need to use a compressor to pressurize the upper chamber to move the piston fully down then continue as usual?

Is it common for the piston to stick like this?

Thanks

Jim