Problem with Network: I have Wi-fi (mostly) but no ethernet.

I have the Eero 6 Router and Netgear CM400 Modem.  Everything has worked perfectly for years. In the middle of a program Roku went back to the home screen and said “disconnected”.  Turns out that all of the ethernet connected computers and devices were now unconnected.  Wi-Fi does work, although it drops out now and then.

Did the usual reboots of equipment which didn’t help.  Windows Troubleshoots says, “doesn’t have a valid IP configuration”. I note that none of the equipment or devices connected to the ethernet or wi-fi have changed or acted up until now.  I also saw this alert when waiting for this web site to load (using wi-fi) "DNS address could not be found" although the site did load shortly thereafter.

Would appreciate any thoughts or guidance.  Thanks

pbroughton

San Diego ("cox north, san diego county)