I have a T5i and my pop up flash is not flashing, i would like to know why?

[Ronaldn]

My flash on my T5i is popping up but not flashing, could someone please advise why?

[ebiggs1]

The flash tube can and does burn out.  It is replaceable by a service tech.

[RobertTheFat]

Here's the dilemma: the best "normal" lens for any of Canon's APS-C cameras is the 17-55mm f/2.8. But that lens is so large that it casts a shadow in the area lit by the pop-up flash, rendering it useless. And the trend towards larger and larger lenses shows little sign of abating. So if I had a Rebel whose pop-up flash crapped out, I think I'd put the money necessary to repair it towards an external speedlite instead.