open the boot and on the right hand side you need to remove that panel, there is a solenoid that drives a pin up and down for the petrol cap release.
Either that has gone or is stuck, I took the cover off the solenoid and the cogs are made of plastic and when used repeatedly small pieces come off and get stuck, a few small sprays of WD40 and a small paintbrush and it started working again, been fine since
