Q: How do I get sound when playing a video? (all other sounds work, just not videos)

Does anyone have any advice as to why I get no sound on my iphone6 when trying to watch a video on Facebook, or a video that someone makes and sends to me?  I have reset settings, gone on forums and followed advice, initiated facetime to check if that works.  All other sounds work, but not that, and clicking on the volume in the bottom right side of a video does nothing either. I have also restarted. Even videos I have recorded have no sound for me, yet when sent to others, there IS sound. So sound is recording but not playing back.