the flash in my lumia is not firing every time,it stops after 2-4 shots.and after that i have to restart the phone to make it work again, it did a soft reset also ,that also is not helping....
Have you tried waiting a bit, even with a camera the built in flash or stand alone flash can take some time to recycle before it can fire again. And if your phone's battery is low it will take even longer to recycle or won't fire at all.