I'm pretty sure I've narrowed this issue down to just premium videos. When I click on a premium video from a search nothing happens at all but when I find the same video through the shows lists (Playdate/Unprofessional Fridays) they start fine. I first noticed this when going through the Life is Strange playthrough. When searching for Life is Strange the videos worked fine until the episode "Playdate: Life is Strange (11/20/2015)" which is when the videos went premium. I've also recreated this searching for Unprofessional Fridays.
Device: Apple TV 4K (A1842)
Giant Bomb App: 2.0.4