My set up is simple:

modem > main deco > tplink switch Ethernet > (3 different pcs Ethernet) 

I have other decos connected to main over WiFi. The issue happens when I turn off my Linux computer that is connected to the main deco via a switch. When this is turned off then the led on deco goes red no internet, I unplug the switch from the deco and  the light goes green but no internet returns even WiFi at this point has no internet.