in the trunk there is a handle under the carpet labeled gas - pull the cord. Then check theprobably blown fuse for the gas door solenoid that pops open the gas door. lol
You'll have to pull that inner plastic off near the gas door to access to solenoid. If it's clicking it's probably trying to work, so you'll need to investigate why it's not popping. I've seen them jam when one of the tabs gets bent slightly.
Pull the cable to release it...however I've seen these snap on foxes due to age. Mine broke, so I need to replace that.