PRS1 humidifer stopped heating

First - thanks to many of the regular poster as i've learned may things on this site, I'm mainly a reader here. I'm about 2+ years into CPAP and my experience is good.. AHI regularly < 2.0. My DS750 humidifier seems to have stopped heating and the DS750 (v2.01) will not respond to attempts to set the humidity value (0-5 scale). Had recently been traveling w/o humidifier and reattached it upon return. problem didn't start right then. for a day or two still had control of humidity (on dial at least). I've repowered everything, reattached the humidifier several times, and explored in the setup menus. I also don't see evidence of the humidifier when in the setup menu... other than a trip to the repair shop any suggestions?

Sounds like you've checked most of the things I would. If it doesn't think there's a humidifier, there's something wrong in the connection between the blower and the humidifier.

Since you're not getting humidification anyway, it seems like trying to repair/replace the humidifier is the first step. If that doesn't work, then there's a problem with the blower, which is more of a hassle.

If it was a S9 I have a spare humidifier.

You can buy a "new" used one from secondwindcpap.com for $70 I think. New plastic water tank. I got PR System One 50 series humidifier a while back from them and it looked brand new.

I don't know about fixing...most of the time we can buy a replacement for less than fixing cost unless someone knows someone who can do that sort of thing and I don't.

Perhaps check with DME store to see if they have one you can attach to your blower to make sure that the blower isn't the problem.
Sometimes they even have spares in the back room.