Watching older Smithsonian episodes, and after watching about 35-40 minutes, they are cutting off before ending. Screen comes on saying “You are not authorized to view this video” and tells me to sign in with my TV provider. This is not prior to watching the video, it’s after watching half or two thirds and it suddenly cuts off, and the ‘not authorized’ screen appears. Has happened with three different videos.
For more information about that channel's features and functionality, you'll want to contact the channel provider support directly to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.