So that didn't work, but it might be OK now. There was no DHT-S517 under A/V, it was under audio, and that couldn't control my AVR S760H at all. So I tried DHT all models under A/V but that was no better, nothing worked at all.
I changed it up under A/V to use AVR Series Main Zone All Models (Essential Commands Only) (Receiver/Preamp). And that seems to work better. I only got to it today so maybe the updated app helped? It seems to turn on and off fine, and volume too.
I'll need to see if it works over time as I have a projector so I can't be using the on/off macro to turn everything on an off constantly, so I'll just see how it plays out.