Problem with Paintball to Regulator Adapter

Good afternoon,
I decided to take the plunge and setup a keg system. I already have a 20oz paintball tank, and will want to take my setup with me at times, so I figured starting with that would be the way to go. I only plan to have 1-2 kegs at a time, so this should be suffecient in that department as well. Not to mention the cost savings of not having to buy another tank at the moment.

That said - I bought a paintball to regulator adapter off of ebay, attached it to my regulator, and screwed it onto the paintball tank and.... nothing. I've done everything I can think of from swapping out the o-ring, tightening as much as i can with a wrench, even putting it on without the regulator just to see if it depresses the pin valve, and nothing. *note, i can manually depress the pin valve, and it does work in a paintball marker.

It just seems that it doesn't screw down far enough for the adapter to depress the pin. Has anyone tried this setup and ran into similar problems? Does anyone have some ideas that I haven't tried (other than buy a 5lb tank and forget it?

I found the issue, and for the benefit of anyone else that runs into this problem and stumbles on this post, I'll post it here

Apparently the end of the connector on my co2 tank was just slightly too large to fit down into the end of the adapater. So, I cut the old o-ring off, took a little 120 grit sand paper, and carefully, and evenly, sanded around the tip of the co2 tank. Put a new o-ring in, screwed on the adapter, and had a perfect fit.