@ReneB. Normally, the Deco system will recommend the client device to roam to the closest Deco unit when the device is moving around. However, whether to roam or not depends on the device itself....

@wong94sp Hi, When the Deco has a flashing red light, it means Deco is disconnected to the main Deco. Please try to move the upstairs M4R near to the main Deco, reboot the main Deco, and the slave...

@kaja69 What's the hardware version of your Deco M9 Plus? You can find the hardware on the bottom label. If it's V1, on the Deco app, you can go to the More>Advanced>IPTV/VLAN to configure the Deco.

@francocm Here is the compatibility list of the Deco M9 Plus, if your smart plug is not in the list, it may not work with Deco M9 Plus. https://www.tp-link.com/en/Deco-M9-Plus/compatibility/

@RyanEverhart789 Hi, In your case, is the network jack that you want to connect the second Deco is connected to the main Deco on the other side? If yes, you can connect the second Deco to the network...

@ponnurz Hi, In this network diagram, the extra ethernet port on the Deco units still works when Deco works in the AP mode.