Sudden Connection Fail!

Hello,
I have a Roon Rock Intel NUC which has performed perfectly since day one. However, today, I moved it to a different network switch - I only have one network here. I can no longer connect any of my remotes. I normally use an android tablet which works well, but I can’t connect my Win 10 Remote either.
The remotes all find the Core straight away, but then when I click ‘Connect’, I just get the Roon Login or Sign Up screen, rather than the Remote just connecting. The first screen gives the corrwect info about the core and says it’s Ready. I have tried logging in, but then I just get the info that I already have one Device setup as a Core.
I even tried Resoring a Backup which is at the bottom of the Login Screen, but that just takes ages and then we are back to the same thing!
I am tearing my hair out here - nothing has changed except the ethernet connection on my network. I can see the Core easily and have tried restarting everything, but I can’t get any of the Remotes to connect to the Core, even though it is ready and available!
I really need some help here!
Tahn kyou,
kind rtegards,

Mike Anderson.

If it’s asking to deauth do that and then connect again