I had the same issue trying to watch the Thursday night NFL game, no sound and took a long time to load the game, it just gave the dots across the screen like it was loading for about a minute. How long before you got sound, out of curiosity? I have no issues with 4k audio or video on Netflix or Amazon prime through the X1 box.
We definitely didn't wait that long. I am curious if it is like that every time, or did it just happen that once time for you?