I'm currently experiencing connection issues with a Verizon LTE Extender, and I have recently purchased a TP-Link ER7206 to help diagnose and potentially resolve the issue. I changed over from a Ubiquiti ER-X just as a sanity check to see if a change in topology would make a difference with the situation. I'd very much appreciate any assistance or guidance on how to set up and troubleshoot this scenario insomuch that the ER7206 seems to be missing some additional diagnostic facilities that I feel could help assure me that traffic is both coming in and going out to the appropriate device.

Background Information:

1. The Verizon LTE Extender connects to Verizon's Security Gateway (SeGW) server via an IPsec tunnel.
2. The LTE Extender is connected to our network behind the TP-Link ER7206.
3. The LTE Extender is unable to establish a connection with the SeGW server. The device logs only show the SeGW IP address and connection failure.
4. We have tried using an Ubiquiti EdgeRouter X (ER-X) previously but were unable to resolve the issue.

What we have tried so far pre-ER7206:

1. Disabling the firewall on the ER-X.
2. Using `tcpdump` to capture packets between the LTE Extender and the SeGW server.
3. Running a traceroute to the SeGW IP address, which resulted in no responses from any hops.

What we have tried with the ER7206:

1. "Nuclear option" - Placed the Verizon LTE Extender on the DMZ just to see what might occur - same result, no connection.

Given the above information, I would like to ask for guidance on the following points:

1. Setting up the TP-Link ER7206 with the Verizon LTE Extender: Are there any specific configurations or settings that we should be aware of to ensure smooth  / guaranteed communication between the LTE Extender and the SeGW server?   
2. Utilizing the DMZ functionality of the ER7206 to help diagnose the issue. Is it possible to place the LTE Extender in the DMZ to rule out any potential NAT or firewall issues? I thought I did this and I assigned the specific Verizon LTE Extender's IP as the recipient of the DMZ assignment... I just want to be sure I'm not missing something since I don't see a method to use `tcpdump` or any similar tooling on the ER7206.    
3. Configuring the ER7206 to capture and analyze packets between the LTE Extender and the SeGW server. Are there any built-in tools or recommended methods for doing this?    
4. Any other tips or troubleshooting steps that you might recommend to resolve this issue?

Thank you in advance for your help and insights.