Not connecting directly do router through wan port

I have an A1143 that I am trying to connect directly to my Netgear MR1100 AT&T FirstNet hotspot. I am using the ethernet port on the MR1100 and connecting to the WAN port on the A1143 with a 10ft Cat6 patch cable. The A1143 is not able to pull an IP address from the Netgear MR1100.

However if I connect the MR1100 to a unmanaged switch like an 8 port D-Link and then connect the D-Link to the A1143 on the wan port, the A1143 is then able to obtain an IP address.

Why is this. Our remote fire stations are changing out from the Cradle point ibr650-150m’s to the netgear MR1100 units because they provide more throughput speed.

We were able to connect the A1143 directly to the Cradle point with no issues.