Unbelievable. Once again no audio from the Streambar unless it's from a streaming service. But I think I am finally on to something. We've usually turned the TV on by using the cable remote. When I do, everything comes on as it should, the TV switches to external speakers yet no sound. Today, after a long power outage, I had the same result. So I turned off the TV with the cable remote and turned it on with the Streambar remote. Voila! Sound from the cable input heard from the Streambar. I turned off the TV with the cable remote and then back on with the same control...audio works fine!
So it has something to do with powering up the TV through the ARC input that must "wake it up" and allow it to send audio to the ARC HDMI device. I'm guessing that when we have another complete power outage, I'll have to follow the same sequence.
If I find that this isn't repeatable, I'll post again. But I'm keeping my fingers crossed.