@HarmH Have you checked to which Deco each of Decos is connected, and what is signal strength of their connections? If I to guess, one of the possibilities could be Deco on the second floor is...

@weteamsteve I wonder if you maybe having two different WiFi networks with same SSID and different passwords. One from Deco mesh, another from elsewhere. Your Main Deco is connected to ISP router...

@Rahmat.A I can also explain logic behind guidelines. For initial Deco setup, you need to connect Deco to working home network. Your unifi router provides working home network, so this is where Deco...

@Rahmat.A There is no harm in trying. Just follow what is said on page 5, make sure you power off Deco and old router before disconnecting them, and power on Deco after it is connected to modem. If...

@TP-Link It is no longer just iPhones and iPads, but Android devices, too. Which means: practically everything. I don't know how Deco Product Manager sleeps at night, knowing that.

@tymek Yes, they can. You can connect that way both wired devices and Decos. Your topology will work, as long as switch supports it. See General questions about Ethernet Backhaul feature on your Deco