Unable to add HomeKit devices (multiple manufacturers attempted)

I have several HomeKit devices that work fine. A few months ago, I was unable to add any HomeKit devices. This started with an Aqara sensor (no hub required). Then I tried two other devices from different manufacturers and I get the same error:

"Unable to Add Accessory. To add this accessory to your home, connect your iPhone to your HomeKit enabled router, then try pairing. If pairing continues to fail, reset your router."

I have reset my router, reset my phone, re-connected to the Wifi, called Apple support, each manufacturer and my router manufacturer, but they all say it is an Apple issue. I gave up in frustration, but I am trying again.

Has anyone experienced this?