I’m posting my own solution as it may help others if they have a similar problem with Youtube.

For no obvious reason I found Youtube stopped working. Firstly there was a black screen, then I could see the videos but when I tried to play the video it would freeze.

Firstly I cleared settings from Youtube which didn’t fix it.

I was reluctant to go straight to a factory reset.

I fixed it by doing a ’power reset’, which is simply unplugging the TV from the wall socket for 1 minute. Youtube was working fine again when I switched the TV back on. I’m not sure if clearing the Youtube cache first helped.

It seems to be like computer problems - try a reboot first before messing with too many settings.