Chim, got a few questions for you....
Can you see through the airwick tube?
Is the connector (post) on the OMG dry?
Now...on my video review of the OMG for some reason (have no idea why) the OMG strangely doesn't like some Cartos. I still cannot get mine to work with one of the 3.5ml tanks. It makes no sense whatsoever since both Cartomizers in the tanks are identical. I was able to get it to work a few times briefly by drawing on it while unscrewing it and angle the tank a little.
So as long as the carto and OMG connector posts are dry and you can see through the air tube try this. Screw the tank on and try taking a draw on it as you slowly unscrew the tank.
I think this has a lot to do with the OMG and probably very little to do with you.