My screensaver will not play. I have it set to start after a minute of no activity. I have done three factory resets. It won't work.
So you have done a system update, you have also restarted the Roku, you also have cleared the cache completely, and you have unplugged completely the Roku for about one minute and then plugged it back in, and it still does this ?
Try choosing any other free screensaver and seeing if any of them work maybe ?