Nighthake M1 M1100 NAT Harpinning Issue

[Raffyy]

Hey all, after 23 hours this issue has me beat. 
The very brief version is I am trying to set up a Communication Service called Unity Intercom (that runs on a Macbook) connected to a M1 Mobile Router. This is designed to work anywhere I take these two items. 

I need to connect the client (iPhones) that function as similar to a walkie talkie but much better, while the iPhone is on 4G. 

After testng on 7 different iPhones I am not able to get the client to connect successfully on all the iPhones. 

This seems like a NAT hairpinning issue. Meaning that the Router is not allowing the device to connect unless that iPhone is on a WiFi network. 

There are way too many aspects to list here that have been tried. 

The Portforwarding is connect, the Dyndns Updater is working, the settings in the client are correct, etc.... 

Has anyone ever encountered an issue like this? 
Would love to know how you got around it. 

Happy to add more detail to this if anyone understands what I am trying to achieve and found a sucessful work around. 

[schumaku]

The M1 is configured as a router, or is it configure for tethering?

Does the mobile provider assign a public IP addess to the router? Otherwise it will be difficult to have the required port forwading (from wally brain) 20101 TCP and UDP to the Mac operating the Unity Server at this site.