If you are having issues with sound when using the IFT app on iPhones please read on:

Please check if your mute button is on (the physical button on the side of the phone)

If the issue persists, please let us review and reply:
1-Does the issue happen with only downloaded videos or also non-downloaded videos?
2-Are you using ear/headphones? what kind are they? does the issue happen when using normal phone speakers?
3-What are your phone details (iPhone model and iOS version)

Please also check the Appstore for any updates to the IFT app and install that.