I have an Olympus MJU 700 but the flash is not working

Hi,
I want you to check these,

Check that batteries are fresh.

Check that camera hasn't been set for no-flash mode.

Give the flash time to charge before pressing shutter.

Try to reset your phone by MASTER RESET(Factory reset) by referring to your manual.

If you updated the firmware for your camera, then that update can also be a reason for your flash not working. so try installing the firmware which was present when the camera was working good.

check there is any debris in the hot shoe, there is a switch on the left that stops the pop up working when you put a external flash on.

If you have been using a speedlite or another flash on the hotshoe lately, there is a little metal strip in the hotshoe (rail) that disables the pop-up built-in flash. So, this little metal strip goes down when you slide in an external flash and disable the built-in flash by breaking an electrical contact. This little metal strip has the occasional tendency to get stucked down after unmounting your speedlite, which results in the behavior you are seeing. Just turn OFF your camera and use a toohpick in the hotshoe and force very gently the metal strip up to make the metal strip goes back to its original position when there is no speedlite mounted on your camera. Compare both sides in the hotshoe (rail). Turn it ON and there you go!

Hope my info solves your problem,
Thanx for using fixya,
Cheers.