Gas cap resisting?

To the OP you will find all sorts of fixes for this problem in the search engine. Loosening the retaining bolts and re-centering the cap in the opening, filing off burrs and sharp edges, greasing the strikers that catch on the tank opening, etc.. I've tried all those but the tommy bar method when this problem started on my 2005 in maybe 2008. None was a permanent repair and the only one that returned the action to that of new was simply lubing the mechanism thru the key slot. Ps88 is an aerosol and apparently gets around inside the mechanism besides the tumblers.

The round part that "pops" the cap up when the strikers retract is probably sticking. If you open the cap and leave it open and then press the ring as if the tank fill opening was pressing it closed you'll see the strikers release to lock the cap down in place and the key snap rotates 90 degrees to "locked". Turn the key to unlock and watch the ring pop into the "open the cap" position. If it's not popping down the strikers do not fully retract and the cap sticks closed. If a knife blade raises the cap after the key unlocks it then the strikers are retracting but the ring does not pop down to raise the cap free.

Whatever works for me may not work for you. I lubed the mechanism and worked on freeing the ring part of the mechanism from the underside. After that I've not had a problem in well over 100,000 miles.

Larry Igofar was a lot of help over the phone, I know, no one here is surprised I'm sure. I completely tore down and rebuilt gas cap, I should be good to go, thank you all.

When the assembly is new it has a light coating of grease in the bore which holds the lock assembly, some folks spray oil, break free, triflow, WD40, etc. Into the keyhole thinking it's a good thing. What that does is flood the bore and dissolve the grease and over time it collects dirt and debris and starts sticking.
The best fix is to gently lift the rubber seal and remove the large plate washer underneath it, you will then find some small his screws, remove these and the assembly comes apart. Be sure to leave the key in place to hold the tumblers or you will have them drop out on the table! Clean then place a small amount of silicone grease in the bore and reassemble in reverse order.
Your lock will work as new again.
It's ok to use graphite or lock specific lube on the tumblers, just do not use enough to wash out the grease.