Internet connection to switch from Gold Plus

Hi Team FW,

I'm not massively technical, so please bear with me.

So the first part of my topology is fixed, as in it has to stay as it is:

ONT > Vodafone Power Hub (everything off,  acting as modem) >

Then it's:

> Firewalla Gold Plus (router mode) > TP Link Archer BE230 (access point mode)

TP Link is on Port 1 of the FWG+, to the WAN port of the TP Link. If I run an ethernet cable from the TP Link to an unmanaged switch, TP Link loses Internet.

If I instead run a cable from FWG+ Port 2, TP Link loses internet. (I have two other TP Link routers, AX55 and AXE75, which I have tried with the same results.). 

I created a separate LAN (LAN2) on FWG+ Port 3, then plugged the switch into that. The devices connected to the switch report no internet. TP Link on LAN1 still has an internet connection without any issues, so wireless devices are fine.

I feel like I am being stupid, and I must be missing something simple.

Thank you for taking the time to read my post. Chris