Help with Network problem. Flakey when not accessing Pi using PC web browser

When I’m using my linux PC to access HA on a RPi4, everything is fine. I can have a web page open for 12 hours and its good. I can use my android phone or dashboards on google smart displays to access everything. It all works. Everything is connected by LAN cables. It all used to work.

As soon as I shut down my linux PC, I start getting connection errors. Various devices time out, or disconnect.

I started using Nabu Casa to try and fix the problem.

Settings->Home Assistant Cloud->Remote Control URL is set to


Settings->System->Network->Home Assistant URL is set to

Internet ON Use Home Assistant Cloud
Local Network OFF Automatic

where XXX.XXX.XXX.XXX is the local IP address of the Raspberry Pi4

What am I missing???