My TV has no sound at all on any channels, apps or catch up. We’ve reset the box twice (leaving it for 10 minutes each time), checked the HDMI ports, reset the WiFi with no results. We haven’t been able to watch TV for two days and I can’t think of anything else to try.
You say you've checked the HDMI ports. Have you tried a different HDMI cable, and also different HDMI ports on your TV as well?
Earlier this year I had no sound at all on my V6 box. I tightened all the cables to no effect. I then decided to spring clean as it was like spaghetti junction behind the TV. I unplugged all cables from all equipment, TV's computers, Switch, V6, router. When I plugged everything back in the sound was working on my V6 and I've had no issues since then.
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali