This is a little counterintuitive if you’re used to the fuel release lever being inside of your vehicle, but it’s actually a pretty common gas tank security method for newer vehicles. It should be noted that this vehicle’s fuel door locks when you lock your car, so potential thieves or saboteurs won’t be able to access your gas tank without first unlocking your vehicle.
If you have any further trouble opening your dad’s vehicle’s fuel tank, it’s possible that this Buick is experiencing some electrical issues and the locking mechanism isn’t functioning properly.