HomeKit accessories not pairing with new routers

I have used Apple Home for a number of years, however about a year ago my accessories, especially the security cameras quite working, Phillips Hue and Nanoleaf bulbs quit as well. Efforts to get them back up and running failed. I determined that one of my mesh routers had failed and decided to replace them with more up-to-date routers supporting WIFI 7. I first installed Eero Max 7 routers, but I still couldn’t pair accessories. Following conversations with Eero support I was told that they did not support HomeKit and was advised to either go with their WIFI 6 or 6E alternatives or another router company. Following a web search it seemed that the Linksys velop 7 rougher should work and I installed these, however I am still unable to pair accessories.

I have great access to the internet with great speed (I have a GByte fibre connection). The Lutron Caseta wall switches have always worked great throughout this. I am at an impasse. How do I get these accessories working?

[Re-Titled By Moderator]