I own one. You've got some crap in there around the 12 gram face seal. I'd clean it and then follow the rest of this post.
This post is long and is a detailed takedown instruction for the PT Xtreme only. Do not use for any other PT model (I can't promise it will work), and do at your own risk.
We're gonna have to remove the whole valve to get a better look at the whole thing.
If you don't know how to do it (Not trying to be a dick, but to set the record straight.), here's a quick rundown:
1.) Remove all sources of air, i.e. de-gas the marker, and de-pressurize the marker. Dry-fire once to confirm the marker being empty.
2.) Remove Barrel, and Magazine.
3.) Remove the 3 screws holding the grip in place. 1 in the rear, 1 in front, and 1 underneath the finger guard.
4.) Remove the Quick-pin in the rear and til the marker onto a workbench surface. It should not be stuck, if it is give it a slight tap.
5.) Remove the odd shaped screw on the bottom of the marker. One of the screws from the handle uses it to hold onto the marker. It should use a relatively large flathead.
6.) Take a long, narrow flat-head screwdriver and push it down the rear of the marker on the bottom tube, trying to avoid the walls or the pin retaining pin.
7.) The valve should fall out where the 12 grams are pierced and you can play with it now.
Now take a look at the three o-rings on the outside of the valve. If they are intact and are able to be twisted a bit without shredding into pieces, we're good.
Now try to open up the valve where the brass pierce assembly is. If it doesn't budge or it seems like there might be what looks like rubber caught in the threads, you will need a penny and a dremel for the next part. I cut a penny to fit the slots and put an allen key through the valve a bit and twisted it until it came off. Put the penny in a vise, much easier.
If there was a shredded o-ring in the assembly, it would be indicated by the inability to unscrew the pierce pin. One more seal to remove and replace.
Lastly, Once you have the little cap out of the valve, it's two brass pieces twisted together. Take a flathead and your penny, and twist them apart. Try hard not to loose anything. Then push out the pierce pin and the screen filter.
This should finally give you nothing put a flat rubberized seal. This is the part you will more thank likely need to change. There is not widely available replacement for this part. You can make one or special order one. I've been making them personally.