Support responded to me again this evening. They think I was running something older than the 20250815 firmware ; they said

"One of the issues fixed in the new UI version was that it was not properly alerting at startup when there was a firmware update available."

So - for me anyway - things are ...

I sent them an email this evening and they did respond. Their latest reply asked me to reboot both the Flex DUO and my Mac. I did that and now everything does appear to be working. The guide info is there and I was able to start a recording while watching the live tv window.

I'm still confused ...

I am seeing the same thing this evening. The app was not working at all (I use it on Mac OS and also Android) ; I was getting "Error invoking Client Start". Now the app is working and it DOES see my recordings (and it can play them) and I can watch Live TV but there is no guide information available ...