Hatsan Lightning Not Building Up Pressure Need Help.

I purchased a hatsan lightning a few months ago since then ive only used it twice. The compressor has been sitting unused for about 2 months. Today i was testing it and the pressure reading on the digital gauge is stuck at 290 psi im not sure if the digital gauge is faulty or if its the actual compressor itself that is not build up pressure. Any help would be appreciated to try and diagnose this.
 
May be its just a bad pressure gauge. You probably have done it but I would suggest hooking it up to a rifle with empty cylinder and check the pressure reading on the rifles’s gauge. For my Yong Heng, the only cause of failing to build up pressure has been leakage. As your compressor has a much higher flow rate , any leakage should be audible. If you are sure that there is no leakage then something is wrong inside. As your compressor is so new, its unlikely that the piston rings have failed. I will check the check valve between the first stage and second stage, then the reed valves at the top of the cylinders. May be something is preventing them from closing fully. Good luck.