gas filler flap

Try very gently pressing on in fuel door while simultaneously pulling the backup fuel door cable as sometimes the plunger gets stuck on the striker plate. If that doesn't work, I would raise the car, remove the wheel & fender wells and have a look at the solenoid to see if the plunger is stuck. It sits in a bracket attached to the filler opening area and sits high inside the bodywork, but you should be able to see it.