FortiExtender not working in IP Passthrough mode

[jokes54321]

We bought two 201e models 13 months ago and put them on a shelf for emergency purposes. Today I had a need to ship one out, configured to be managed Locally (not via FortiCloud or Fortigate) and using IP Passthrough. This was working fine on the base 4.1 that came with the extender, but I needed the ability to remotely connect to it via the LTE interface. 

I saw that as of version 4.2.2 they added this functionality, so I upgraded the firmware to 4.2.3 along with modem firmware 19.1.0. After applying these, the FortiExtender will no longer pass the LTE IP address through to the Fortigate behind it. I also noticed the blue gear icon no longer lights.

I tried downgrading the firmware back to 4.1 and the IP still doesn't pass through to the Fortigate. Unfortunately the support contract expired on this last month, so I'm not able to contact them.

Does anyone have any ideas? I really needed to ship this today and I'm afraid I won't make tomorrow's shipping either. I'm starting to think a Cradlepoint might have been a better choice since they're very mature in this space. 

Denny

[jokes54321]

I got this working. I'm not 100% sure it was the proper way to fix it, but it did start working the way I expected it to. 

I don't recall what screen in the GUI I found it on, but there was a spot for a Virtual Wire pair for the LTE interface. I mapped this to port4 and it now consistently passes the IP through to the Fortigate. 

Denny

[ezhupa]

You can refer to the below documentation for more information regarding IP Passthrough mode for FEXT
https://docs.fortinet.com/document/fortiextender/7.4.1/admin-guide-standalone/123612/ip-pass-through....