Can't make calls using 4g LTE Cellspot

I had a Verizon Network Extender before switching to T-Mobile. The Network Extender was working fine. After switching to T-Mobile,  I set up the T-Mobile 4G LTE Cellspot using the same network connection to my DMZ (no ports blocked). 

I have a very fast fiber connection and typically one-bar of service from T-Mobile on my Samsung S22 Ultra.

After initializing, all the lights stay lit (except for the 3G light which I understand will never light).

After a short time, the 4G LTE light starts to blink and  eventually shut off, when  the status light turns blinking-amber. After a short while the status light goes solid-green again and the 4G LTE light turns solid-green.

This constantly cycles thru the same sequence. At no time am I able to make calls with WiFi calling turned off. 

T-Mobile replaced the first unit I had, thinking it was bad, but the second unit does the same thing. 

I’ve tried moving the Cellspot to a different location with the same result.

So far, customer service hasn’t been able to help.

Any suggestions would be appreciated.