Chosen Solution
No audio on videos but can hear through speakers
Go to your home screen, and press Volume up or down. Do you see “Ringer” or “Headphones” or something else? If its headphones it means that you have something in your headphone jack that could make your phone think there is headphones in which will not let you have sound. Are you connected to any bluetooth devices? it could also be playing through that.
There was something blocking the ringer switch (perhaps lint/fluff) which made it think it was permanently off. The same can happen with the headphone jack.
First you have to remember while you press volume keys there shows ringer volume label but notice there shows headphone volume label. Definatelly that is the fault of charging flex on which headphone jack connected.Check it and post result.
