Connect router to gateway in bridge mode

Hello!

I have an Netgear Nighthawk (R7600) router that I want to use to provide WiFi, instead of using the gateway. I was following this guide: https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode

The router is the only device connected to the gateway, but it is not able to connect to the internet. I power-cycled both devices, waiting 10 mins for each device, and no luck. Is there an additional configuration for the gateway to support this configuration?