Double NAT Problems? T-Mobile and Konnected

I'm setting up a brand new network with a unifi controller, 4 AP and a 48 port poe switch (usw-500-48).

One of the first things that I did, was connect 3 separate POE Konnected Pros (alarm control boards).

All 3 boards power up and LEDs on the boards seem to indicate no problems.

Even after rebooting etc., only one of the three boards shows in the ubiquiti software. The other 2 boards (which are successfully being powered by the Poe switch) don't show any device connected to the ports that they are being powered by and are not discoverable in any other systems (Home Assistant in this case).

Here's the kicker that may or may not be important: We have T mobile 5 G internet and a G4 AR gateway. It does not permit bridge mode and BYOD is not permitted unless switching to a business plan. I know that double NAT is bad. I'm not terribly technical, but I understand that UPnP is important to how these boards work (https://support.konnected.io/device-discovery-troubleshooting) and double NAT can affect UPnP.

1. Can anyone say whether it's likely that double NAT is causing this problem? It seems odd to me that one board works and the other two do not in the same network.
2. Any ideas for the not terribly technical on how to fix, ideally preventing problems down the road if possible?

TIA!