I just purchased a Fuji GS645 and I can't get the flash to work. Is there some trick to it? I put a cheap X sync "Achiever" flash on it and it wouldn't fire. I figured it wouldn't work with my Nikon SB50-DX, but I'm hoping there is a ISO to TTL adapter that I can purchase that will let me use it.

Are there separate batteries for the flash somewhere on the camera maybe? I guess I need to get a manual for it.