Marlon Humphrey absolutely committed pass interference on DeAndre Hopkins, a fact that looks more obvious after seeing it multiple times. The result of the play was the Texans were stopped on a fourth down attempt instead of getting the ball on the one yard line. It was a big moment in the game, at the time. It ended up being inconsequential because the Ravens were winning that game convincingly one way or the other.
The NFL has put themselves in a bad spot with pass interference challenges. They almost never get overturned which makes these challenges a waste of time, something to go through the motions of, with an almost predetermined outcome.