If you see this message, below, that means that the Stream+ is recording 2 programs.
"This channel can't be played until XX:00 PM because other channels are being recorded."
The Stream+ has 2 tuners. If you are recording two programs, then you cannot watch another live TV program on a 3rd channel.
However, you can watch a previously recorded program, or content from one of your apps, like YouTube, Google Play Movies/TV, Google Play Music, Google Play Games, or another app that you have installed.