iPhone 15 will not consistently connect to wi-fi through Eero mesh system iOS 17.5.1

A few months ago, after having Eero work consistently for years, our Apple devices, primarily but not exclusively, iPhones, stopped consistently connecting to wi-fi. Wi fi is connected on some devices, but the phone itself reads "no internet connection." I have upgraded my iPhone (going from a 12 to a 15), upgraded our Eero system, reset network settings, reset the entire wi-fi system, turned off private wi-fi address, disconnected Sonos as the problems coincided with the installation of a Sonos system, and had AV people come to the house to try to figure it out, but nothing is solving the problem. Sometimes, things will work for a day or two, but then we are right back where we started. Interestingly, the guest network always works reliably. We are desperate for a permanent solution. Help!