Epiphany 3.37.2-48-g95f23a5c9 WebKitGTK 2.29.1 To expand, it goes to the correct page but simply doesn't play a video. It's a black screen with well, nothing, no sound or video, no video controls. Can give logs if necessary due to the A/B roll out that happens on Youtube which might make it hard to reproduce.
This no longer happens, I'm not exactly sure when it was solved or how. Can't reproduce. Might've been related to ad blocking.