We have Ignite and now we have 2 modems; Hitron CGN3 & Arris XB6
Why? Is one a modem and the other a router?
Seems like duplication of hardware. No manuals, etc. to explain the setup.
The CNG3 and the XB6 are both all-in-one modem + WiFi router devices. Rogers will ship you an XB6 gateway when you order Ignite Internet. I presume that you have had the CGN3 for a few years now. You will need to swap out your old modem and install the XB6 in its place. You may also need to call into Rogers to activate the XB6.
For instructions on how to install the XB6, go to: https://www.rogers.com/customer/support/article/how-to-setup-your-ignite-gateway
It isn't absolutely necessary to use the mobile app to install and configure the XB6. In fact if you do, you will lose access to some settings in the local Web Admin UI. To configure the XB6 using a web browser rather than the mobile app, connect your computer to the XB6 and go to: http://10.0.0.1/