Nikon D90 won't fire anymore but it pop-ups no problem

My Nikon D90s flash won't fire anymore! There was no trauma done to it. I've checked the settings and everything looks fine, it's on auto flash but won't flash! I've tried resetting it, still no flash! What could be wrong with the camera!

On Auto it will only flash when there's not enough light to take the image. Is the ISO very high? If so, it may think it's got enough light.

If you set the ISO to 200 (with Auto ISO turned OFF) and you're in a dark room and the flash still doesn't fire, then it sounds like the flash tube is burnt out. This is unusual as it usually only happens when you over use the flash (fast shooting on max power) of it's aged & worn out. Could be a faulty flash tube. If it's less than a year old, should be under Nikon's warranty - contact a local service centre.

Do a Camera reset.

Hold down the +/- and AF buttons (next to the green dots) for a few seconds, and the D90 comes out of whatever crazy mode it was in and returns to sanity. The top LCD blinks and everything is back to normal.