I am surmising that you mean that the LED flashes? Or it just turns on, then immediately off with nothing else happening?
It looks like something is definitely wrong with your 5v line. Look around U5 and make sure that nothing is solder bridged together, although I believe that is the one IC that is already soldered onto the board. Also make sure that D19 is soldered in the correct orientation, as well as D20 if it is used. If you don’t have a D20, make sure that nothing is soldered to R13.
It is possible that your U5 is damaged, but I would look at everything that is involved with U5 first. IE make sure that you have 12 volts at Pin 5 of U5 etc.