I have been using this Deco Mesh WiFi system for almost one year and had almost no major issues...until last week.  I have Verizon FIOS internet and my previous configuration was 

VZ ONT via ethernet --> Deco Unit (Main)  + Deco Unit (Satellite). [6ghz is providing backhaul]

Last week, the deco unit connected via ethernet to the Verizon ONT keep showing no internet connection. 

I tried everything from rebooting several times, factory resetting, swapping the deco units, changing ethernet cables, changing DNS server to public DNS servers and still none of it worked. 

My understanding is that the Deco system uses an auto sensing wan/lan technology which may be causing the issue.  

My current (temporary) configuration is:

VZ ONT via ethernet --> VZ Router (wifi disabled) -->Deco Unit Main + Deco Unit (Satellite).

This temporary configuration works but is much slower.  I also DO NOT want to switch the Deco units into AP mode since Ill lose all the features of using it as a Router.  I would welcome any help to resolve the issue so i can stop using VZ's router and return to my previous config.

Please help!