Hi,
I use the OSMC skin. I’ve had this issue since we got the Vero, in the YouTube and Twitch add-ons when I press OK or Play on a video it won’t play it, however if the video is added to favourites it will play from there. I did get around this by opening the menu on the video and pressing Play from there, but with the update to Nexus the Play option has disappeared and there is only the option to choose quality, play with subtitles, etc, making an extra step to playing the videos which has gotten annoying.
I searched around and I couldn’t find anyone else with this problem so I wonder if mine’s messed up somehow. Thank you for any help anyone can offer 
Can you switch to the Estuary skin and see if the problem also exists there.
In Estuary, it works if I go to the add-on and browse to a video. But if I go to Favourites and go to a channel I favourited from there it doesn’t work.