LG TV won't play HD audio

Nov 12, 2018
I'd be very grateful for any help.

I have an old HD TV (it's an LG about 8 years old) but I can't actually get the model number easily because it's mounted to the wall. It hasn't been used much and is in full working order.

It has writing on the bezel which says "Full HD" so I'm pretty sure it's 1080p, but when I plug my Sky Q mini box in to it, only SD channels produce audio.

Both SD and HD channels have a picture but audio only works on SD channels. Any one have any idea on what's going on or how it can be fixed?