Hey  @doublev1234,

Assuming you are looking to use the Decos in Router Mode and not AP Mode. If you believe that everything is properly connected, I would first try changing the used ethernet port on the Deco to see if there is any change.

Also, is your switch connected to your Nighthawk or Your Deco? It will need to be connected directly to the Deco, and the Nighthawk should only use one LAN Connection. (2 Total - WAN from ISP Device and LAN for Deco Netowork. If it is connected to the Nighthawk, your Deco and switch will fight for the one IP address the Nighthawk can give in this mode, causing disconnects. 

You will want to have all your networked devices 'downstream' of your Deco network.(ISP > Nighthawk > Main Deco > Switch + Satellites and Client Devices)

What model of the Nighthawk are you using specifically? Was it provided by your ISP? 

From what I can quickly tell, this is another router and should be able to be removed from your setup entirely - allowing your Deco to communicate directly with the device from your ISP can help take additional potential causes out of the equation.