CBR40 as access point with Xfinity modem router set up

[Surg]

Hello, I could really use some help.  In an attempt to improve my internet service for work and provide WiFi throughout my row house, I switched to Xfinity (only service available) and purchased a RBK50.  I'd like to use the RBK50 as an access point, but can't get it to do anything except power on.

Current set up: Xfinity modem/router connected to wall cable via coaxial cable

RBK50 connected to Xfinity modem via Ethernet cable

I am able to get internet access and set up an Orbi network in my home, but I am unable to do anything else like connect to the Orbi satellites.  The power light on the Orbi is solid blue, and the downstream light is a flashing blue.  Neither the upstream nor LED lights come on.  The ring light on the top of the Orbi is magenta.

Is my only option to omit the Xfinity modem/router altogether?

[FURRYe38]

You should post this here since you don't have the cable modem Orbi system:

https://community.netgear.com/t5/Orbi/bd-p/Orbi

Modem Combo Units:
Couple of options,
1. Configure the modem for transparent bridge mode. Then use the Orbi router in router mode.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.
3. Or disable all wifi radios on the modem and connect the Orbi router to the modem, LAN to LAN and configure AP mode on the Orbi router.