@OMGChris This is correct: the next step is to switch Deco mesh to Access Point mode. You do not need to move Deco units for that or change network layout in any way, just make configuration change...

@dkw92 Check if IPTV enabled accidentally, and disable it if it is: https://www.tp-link.com/en/support/faq/2421/ Enabling IPTV is the only way to disable second Ethernet port on Main Deco I can think...

@dkw92 Connect all three Deco in daisy chain mode, using Ethernet cables that connect Satellite Decos to the switch: If Satellite Deco can't establish Ethernet link to Main Deco (and to be sure, then...

@OMGChris If you go directly from modem to switch, you can only manage hardwired to switch devices through modem/router management interface. That might not be an ideal solution for you, but if you...

@OMGChris There are two options to try: 1. Swap Main Deco with one of Satellites to see if it is Main Deco hardware issue. You can do that by following the process of promoting Satellite to Main...

@Saadyc It may help if you tell names of Deco models you have and switches you use. Meanwhile, check this document: General questions about Ethernet Backhaul feature on your Deco