My 05 MC has 64,000.00. The gas tank cover will not unlock. Has anyone else had this problem? Both doors unlock fine remotely and using the toggle.

 

There is a manual release you can access from the back "tool kit" access hatch.

As for a cause, well, there is a connector under there that is for the unlock solenoid. It would not have fallen out. The solenoid might have gone bad. A lazy fix would be to disconnect the solenoid's wire and then tape the manual release back. You will be without a locking gas cap though.