Hi all. Just bought an used P7100 in good condition. Very pleased for now but I have one problem: the flash pops up but does not fire. When it's popped up and I press the shutter button, the light on the left side of the viewfinder becomes red and everything works well, only the flash doesn't fire. I've tried all I could think about but nothing. If I put a SB600 it works well, but with its built in flash nothing. Any suggestions or do I have to send it to service. This is the only issue the camera has.