As others have said we need some more details to help... Here's a first crack at it though:
First. Did you disassemble/reassemble the marker recently? If so, did you push the bolt forward before closing it up?
Now for the different possible air options:
If using a 12 gram in a magazine? I can thing of 2 simple possibilities:
1 - The 12 gram isn't fully piercing, try tightening the 12 gram change knob on the magazine a bit more.
2 - The marker is setup for remote-line/rear tank ASA. When setup for constant air there's a blocking nipple in the magwell. This can be user changed during a standard maintenance disassembly.
If using a tank on the rear ASA?
There's an on/off knob on the side of the rear ASA. Try adjusting that after putting on your tank. WARNING - If the marker is setup for 12 gram mag use your entire tank may dump through the air nipple in the magwell.
Using a remote line?
- If using the remote line port on the bottom of the ASA and you can't get air to the marker it's either that the bolt wasn't pushed forward during reassembly, or something is gravely wrong.
You implied twice that you don't know anything about the marker. So I suggest finding the manual and reading up a bit.