ORBI RBR50 router - Unable to access HOMEKIT outside of home network

I am successfully using Apple HomeKit with an ORBI RBR50 router within my home network. 

However,  when I attempt to access HomeKit out side of my homenetwork (e.g. over cell connection on my iPhone) all HomeKit Accessories first show change to "Updating" and then to "no response" and I cannot access the HomeKit environment. 

All components are on latest firmware. 

ORBI RBR50 - v2.7.4.24. (AC3000 with two satellites 

APPLE HOMEKIT HUBS - 15.5.1

iPHONE 15.5

I have contacted Apple support and they were not able to identify any issues within the apple collection of components.    They suggested that the problem looked like either the router (ORBI) or the ISP is filtering incoming HomeKit traffic.

I have reviewed other postings in this community but so far I have only found reports of some issues with HOMEKIT/ORBI WITHIN the home network - not external access.

I am NOT currently using the Netgear Armor security. 

If anyone has suggestions as to how I may be able to troubleshoot and/or resolve  the issue it would be much appreciated. 

Thank you.