Connecting one mini box via Wi-Fi and one via ethernet

[Wodehouse+Island]

Hi

I have a SkyQ 2Tb box which is connected to my router (not Sky Broadband) via Ethernet cable.

I have been running two Sky Q mini boxes via Wi-Fi for years quite happily.

I have a third box which I want to instal in a garden room which is way too far away for Wi-Fi, but has Ethernet.

I have turned off one of the other boxes (as I can only have two live at once and have connected the new one to the Ethernet cable, but it doesn't want to connect. It is still coming up with the instruction to press the link button on another box, but then wont connect

Does anyone have any experience with this?

thanks in advance