Upload & Sell: Off
It should be a pretty simple release. Once it is open, a thorough inspection should tell if there is debris or some other issue causing it to stay locked down. But it does require the camera to be turned on so there might be some internal electrical issue.
FWIW, Leighton, I use my built in flash quite often. Whether it is to trigger my 2 - SB800's or just for fill.