Stick with it man... the rewards are awesome. I haven't had that particular problem. Sounds like it might be something in the foster fitting check valve. Have you contacted Mike? Give him a chance to get you up and running. His "no return" policy is only to protect him from people ripping into these guns and doing crazy things to them and then trying to return them. They are tinkerers guns and we are expected to tinker. Altho he won't take them back, he will most certainly not leave you with a non-working out-of-the-box gun.
remove cap and see it you can get air to blow through it...if you need more than your hands to remove cap then there is pressure in the tube..
you won't be able too, once it's under pressure it is too tight to remove...at 1800 you might be over pressured also,
If you can't loosen the tube easily it is under pressure. Screw the power adjuster all the way in and move the trigger group as far back as you can and still get it to cock. Then fire it.
Which with air in the tube means valve lock. The instructions I gave increase hammer strike, which hopefully will get it to actually fire properly.
Sounds like you were very much over filled.