are you forcing users to tap your opened app (to start the video and do something else)?
When the app first opens you haven't set the activate listener, and so the keep awake will never happen. You ought to only do the keep awake when your app needs it, so set that when you play the video, and unset it when the video ends or the user exits the video early.
Use a variable to say whether the system is currently being told to stay awake, then your deactivate function will remain the same, but the activate one would only say to stay awake if it's needed right now.
Thanks Colin. I had thought the activate listener would trigger, but I guess I was wrong.
I've actually refactored the code to explicitly trigger the keep awake when the video plays, and deactivate when the video is done.
Good catch. Thank you.