Connecting Xbox Series S to PC Xbox App

My xbox is downstairs. PC is upstairs. Up to recently, everything has been fine and connected. But now I can't remote play from my PC.

I've done the power down, factory reset xbox, uninstalled, and re-installed the xbox app on my PC. The App connects; I see "started remote play" on the downstairs Xbox, but the PC screen is just black; Nat is open. UPNP enabled in router. Any ideas please?

:)