AllenK wrote As for the switching to my main router rather than one of the other Decos, I've done what you suggested and it now sticks to the decos, but I can't see what makes the switch from one...

@NLSOER It is possible your Main Deco M5 experiences hardware failure of some sort. To verify that, promote one of Satellite Deco to Main Deco. See Changing the Main Unit for your Mesh Network

@AllenK In that case, it would make sense to return P9 set and get different Deco model, or even try different WiFi mesh brand. If going with Deco, I would suggest M5 or M9 Plus. Deco M4R is also a...

@onslash It is hard for me to visualize from your description how you want Deco units connect to each other, to router and to switch. Can you draw a picture to show all of that?

@AllenK Do you still have TP-Link AV600 powerline adapters?

@Swoosh2023 Deco P9 should have worked out of the box. It is very hard to troubleshoot powerline issues, so if P9 can't establish powerline link it makes sense to just return them. Try (check) two...