@KMacD You don't need superior network speeds for printer, so you do have options. Powerline adapters make sense, but only if they can establish connection to each other. You would not know until you...

@vetgat Can't help you much with this, but at least problem description is much simpler now: "Main Deco 2.5Gbps WAN port can't negotiate gigabit speed with gigabit port of fiber modem."

@vetgat What if you swap connections on Main Deco: Fiber - to 2.5Gbps Main Deco port Switch - to gigabit Main Deco port

@ErnstSl Thanks for coming back and telling how mystery was solved. Out of all probable causes that one was least expected.

@vetgat It appears when your Main Deco connected to the fiber, gigabit networking switch loses its Ethernet link to Main Deco. I can't explain why it is happening, but symptoms match. See this for...

@Andwit You can do that. You can also connect devices to both Ethernet ports of Satellite Deco.