Edit: yea, the last two posts in Metadyne Thumper Stuff
will give you detailed info on the at home fixes so far, for the most part at least. below is like a quick guide covering those two posts, in terms of what is suggested that you try to get yours working
LOL smart man
A new hammer and main valve system have came out, but would require you to send you marker back to Metadyne, which, from what I hear, can take months if not years.
I suggest first you:
-Replace all o-rings (especially on main valve and reg piston) with high quality ones (there's a list somewhere, maybe in the other thread, of sizes)
-Fully lube marker, I suggest magnalube although others have had luck with vasoline, etc
Air up marker and see if it works. If it doesn't work for you, move on to following:
-Add inline reg with an reliable sub-300psi output (I use AKA regs, but Joedirt had success using a stock internally adjustable wgp reg, so it doesn't need to be anything fancy, as long as it can handle 200-300psi)
-Remove the middle o-ring on your reg piston to disable your thumper's internal reg (jd used his internal reg for fine tuning, with the inline reg to keep the input from going over 300psi, and you might also want to try this if you're uncomfy disabling your internal reg, although it might become necessary later)
-Setup bottomline so you can use CA and run that to your reg
-Make sure you reg never goes above 300psi! more likely you'll set it around 250-270psi to get the right fps, but just make sure it doesn't get past 300psi or you'll damage the actuating valve
-Make sure to check all o-rings are still good
-Lube everything up (with light lube, not too much)
Air it up and go from there.
If it's still not working, then I'd consider sending it back to metadyne. The inline reg and o-ring switch out solve problems with my original gen 2 thumper and my newer gen 1, which I bought not working for like 125