Yes, it is a not uncommon that I forget that my phone is using cell connection and not connected to my local network (maybe I turned off WIFI temporarily in some other location and forget to turn back on in the iPhone)
Thanks but have turned off Bluetooth and mobile data so definitely using Wi-Fi.
Also only have one network. Phone, rock, nuc, sonore bridge all rebooted.
In the end I had to choose select another core.
That showed me the same single core with a green ready light. I just selected it and all was working.
Sounds like some sort of bug to me.