@davdav I have Sony SmartTV connected to second Ethernet port of Main Deco, works just fine. Not sure what is going on in your network, but it is unusual.

@cgaertner The final test would be to enable WiFi on TP-Link WR841N, turn off Deco mesh and see if connected to TP-Link WR841N by its WiFi everything works as you expect. If it does, you'll need to...

@cgaertner Yes, Deco mesh will provide WiFi. Think about Deco mesh as an attachment to wired only router and that attachment will be used to provide WiFi signal.

@cgaertner I'll answer on what I can. >(1) Buy another mesh system with more advanced configuration features (e.g. Deco PX50??). Don't bother. Different models of Deco mesh may offer different...

@cgaertner TP-Link Deco does not like devices with static IP address configured on them. Even one static IP address per MAC - and you won't see that device in Deco mesh list of connected devices....

@Folkranger I wonder if there is another WiFi network with the same SSID, but different password. For example, the one from your modem/router you haven't turned off. If there is, device may try to...