@Jannek999 I am testing option II ie without a switch just connect first deco to ISP and second Deco via ethernet from first one (no switch involved), same issue. The switches are fine as they work...

@David-TP In both options all 3 Decos go Red. I am using FIOS ethernet (no cable modem or coax), Ethernet coming to house from FIOS NIC. 100Mb connection not Gigabyte etc.

I recently purchased M9Plus and plan to use wired Ethernet to connect all 3 units. But when I try to connect it via ethernet, the units go down in a minute and shows no Internet in Deco app. I tried...