A common problem Apple iPhone, iPad and iPod Touch users seem to be coming across is that when they play a video, no sound is played. Here are a few things that could be causing the issue.
Ensure Volume/Ringer is Turned Up
Make sure the volume/ringer is turned all the way up. Some users have had to open the “Music” or “YouTube” app, play a song/video, turn the volume up, then play the video again to get it to work.
The device may detect something in the microphone jack and fail to play sound through the speaker. Ensure that your finger or case is not accidentally covering the microphone hole while you are recording. Also, clean out the microphone jack using compressed air or a toothpick if needed.
Check the speaker and microphone to make sure it isn’t blocked with lint or other foreign object. A needle seems to work for cleaning them out.
Airplay is On
Ensure Airplay is not enabling a connection to another device. Swipe up from the bottom of the screen to reveal the Control Center, select the “AirPlay” icon and disconnect anything that may be connected.
Charging Jack Clogged
I have not experienced this myself, but some users have reported that cleaning the charging jack works.
Hopefully one of the above solution fixes your issue. Share your experience in the comments section.