I'm in exactly the same situation. I have a T-Mobile SIM in slot 1, Verizon SIM in slot 2, and only the T-Mobile SIM works (in both slots), while the Verizon SIM doesn't work at all (in either slot). I can see the signal strength, I can see that it tries to reach the tower, but I never get a "Cell ID" populated in the form.
I popped the Verizon SIM out, put it into my spare iPhone 8, and it comes right up, and I can send/receive texts across it, so I know it's connected and routing traffic. Back into the RUTX11, nothing. Popped the Verizon SIM back into the RUTX11, removed the T-Mobile SIM entirely, still nothing.
I tried the `VZWINTERNET` and `INTERNET` custom APNs, without luck. Auto APN also fails. Disabling IPv6 and forcing the link on also fails. It will keep looping over and over and over trying to register with the network, and fail.
I spent a couple of hours on the phone today with Verizon, and we removed the RUTX11 IMEI, re-registered (on their end), waited some minutes, nothing. Tried again, nothing. SIM back in the iPhone, works fine. Unregistered, re-registered with RUTX11 IMEI, nothing.
What are we doing wrong here? This is supposed to work, but does not.