Orbi RBK752 Public IP Connection Issues with Grandstream UCM6202

[lostpty]

I have an Orbi 6 (RBK752) WiFi Mesh System in my home network.  Recently I purchased a Grandstream UCM6202 IP PBX.  I have been able to configure the device properly to work within my network without any issues.  I am trying to confirgure the system in order to connect my devices outside my network (remote IP phones and Wave Lite smartphone application).  I am trying to configure the Public IP on the UCM and the port forwarding on the Orbi 6 WiFi platforms, but am not able to reach my external devices.  Do you have any recommendations of how I should configure the Orbi in order to reach external devices on the Grandstream UCM ecosystem?

Note: I would like to note that I have a similar system at the office that works as described and am trying to get my home system to do the same.

[FURRYe38]

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?

[lostpty]

Orbi Router Firmware Version: V4.6.5.14_2.0.54

Internet Provider Modem: Arris TG2482A

[FURRYe38]

Your ISP Modem already has a built in router and wifi. This would be a double NAT (two router) condition which isn't recommended. https://kb.netgear.com/30186/What-is-Double-NAT
https://kb.netgear.com/30187/How-to-fix-issues-with-Double-NAT
Couple of options,
1. Configure the modem for transparent bridge or modem only mode. Then use the Orbi router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ/ExposedHost or IP Pass-Through 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, configure AP mode on the Orbi router. https://kb.netgear.com/31218/How-do-I-configure-my-Orbi-router-to-act-as-an-access-point and https://www.youtube.com/watch?v=H7LOcJ8GdDo&app=desktop

Try option #1 first, if not, #2...

[lostpty]

The Internet Service Provider modem is acting only as a modem.  My ISP locks the modem so their clients cannot change the configuration.

As I mentioned in my original message, this is a similar setup I am currently using at the office.  I am using the same modem but at the office I have a Microtik router.  I have tried to configure the Port Forwarding to the UCM IP PBX network IP, but it does not seem to connect my external devices. 

I´ve contacted Grandstream and they recommend I contact Netgear.

Please confirm Orbi has experience connecting the Grandstream UCM IP PBX to the public IP so my softphone and external extersion work.  My experience with Orbi up to this point has been seemless.  I hope you are able to help me with this last step with connecting my IP PBX.

[FURRYe38]

Confirm that the modem is in modem only mode by let us know if you see a ##.##.###.### address on the RBRs Advanced Tab/Internet section page or a private IP address of 10 or maybe a 192 or 172 address here. 

Did you disable uPnP before setting up any Port Forwarding configurations and set a IP address reservation for this one devices on the RBR?

Disable any PF configurations and try putting the devices IP address into the RBRs DMZ and test.