OK. Success, I think.
Found the PCM (Pulse-CodeModulation, I learned) toggle in an audio sub-menu. Clicked it and the aids jumped to life.
I put on a Marvel movie to check sound effects; the rear speakers from the sound bar worked as well as the front, and the subwoofer seemed to be OK.
I can control the HA volume only from the Phonak app or the aids themselves.
That’s understandable, and I’ll get used to that.
With this setup, though, it seems I can control the soundbar audio only from the SB remote; previously, I could use the TV, cable box or streaming box remotes to work the sound bar.
Does anyone have experience fixing this problem? I suppose I could get a separate universal remote, but the sound controls on the remotes all worked before.
Thanks to all who responded with advice!