@Anonymous User
Welcome to the forum. Could be a few things, but try powering down both box and TV, removing the HDMI cable from both ends, and then reconnecting everything back up again. If you have a spare HDMI cable, try that as well. It's possible it could also be intermittent connection issues, although that would usually be noticeable by varying quality or pixellating picture rather than sound. However wouldn't do any harm to try rebooting your broadband router, making sure the NOW TV box is in an open space (ie not stacked on other items, on a crowded shelf or tucked in an enclosed cabinet) and particularly at this time of year keep away from Christmas lights and tinsel!
If that doesn't help and it seems to get worse, try a factory reset. You'll find the option under Settings > System > Advanced System Settings > Factory Reset (and then enter the code shown on screen to confirm)
You'll need to enter your wifi and NOW TV account details again so have these to hand.
