You probably got some of your oil off your fingers in there. Get a piece of scotch tape and stick and lift both under the film and on the screen to lift away oil/dirt. It should stick like new... Unless you bent the film in which case you need a new one.
I've never had much luck the but prior post is the way to do it. Every time I try to remove dust I end with even more under the screen protector. I highly recommend the shower trick if you're in a dusty environment.