Assuming you are trying to watch the Apps on the 360 box are you only using an HDMI cable or HDMI and fibre optic cable for the audio to the TV, any Soundbar or other audio equipment connected.
If it's straight 360 HDMI to TV make sure the cable is V2.1 or higher and not connected to the HDMI-ARC or HDMI-eARC connection on your TV. If the 360 audio setting is set to Follow content (which it probably is as it's the default) try changing it to one of the PCM settings incase your TV doesn't support the audio format not knowing what TV you have.
If none of the above helps have you tried doing a factory reset.
It's only a partial system reset and not a complete factory reset. You are given 2 options,
Keep Recordings
Format Disk
Choose Keep Recordings, that means you won't lose your recordings and any planned recordings or series links you've set up, you will have to sign into your apps such as iPlayer, Prime, Netflix and ITVX again, also Match frame rate and Standby power consumption will go back to their default settings if you have changed them.