Google devices no longer connect after installing Xfinity, Gen 3

[Tim55]

I recently installed the Rogers Xfinity Gateway, Gen. 3 Modem and now my Google Devices no longer work.

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Wifi extender: I also use Google Wifi, mainly to extend the range of my network.

Notes:  Google Wifi Mesh System, Gen 1.

Problem: 

The Google Mini (x5)- along with many other devices no longer connect after installing the new  Xfinity modem. 

I tried every suggestion- right down to reformatting the Google devices. No success though.

The error that comes up is at the very end of the set up process.
See below:

I called Rogers but they didn't know how to turn off AP Isolation.
I logged into the backend too- but there isn't any obvious way to do this either on this modem, other than turning it to Bridge Mode..

I even called Google Help but they say its beyond their control, its an ISP (Rogers) issue. 
But after calling and texting the Rogers support, all I have gotten was "try Bridge Mode"- which turns off the wifi and effectively just makes the Xfinity a network switch. Thats OK if it fixes things but then my Google Wifi stops working too! 
Prior to adding this Xfinity Gen 3 modem, all of my devices connected successfully and everything worked well. Now its not.

Does anyone know how I can fix this issue? TIA

Here is the error received on my Google Mini setup after a full reformat. 
NOTE: the passwords are correct, the network has been rebooted, etc. 
Turn off AP Isolation

[RussellA]

I had a similar issue with a printer. It was saying connected, but wouldn't print after replacing modem with Gen 3. I had to go to WiFi Details in the app, select edit WiFi details and set security to WPA2.

WPA3 isn't supported by some older devices.