I have a XE5300. Brand new router from Costco. Replace the same model that died suddenly (was about 18 months old). 
 

xfinity outdoor camera now cannot pair to the router. It  worked on the previous router. 
 

I have tried the following

Upgraded firmware

Set the frequency of the network to 2.4 ghz only (but previously it was 2.4 & 5 and I didn't have problems).
Use a WiFi password that does not have special characters. Apparently Xfinity devices do not like that. 
Ran the network optimizer and it changes the WiFi channel from 9 to 2. 
 

I tried the tips from the other thread from 2020 but those didn't work. 

I get to the point where I enter the WiFi network SSID and Password but then I get stuck in an loop and cannot get beyond this screen. 
 

looking for any tips. I had a technician visit and they tried 2 new cameras and neither worked. I have many other devices including a Nest/ Google camera and only the Xfinity cameras refuse to connect. 
 

anyone have success? What are your settings?