There was a pending OSX update that I’ve been resisting doing due to the mess it always makes of all the desktops (really i can’t believe they haven’t created an api for per window per desktop memory), after doing the update, Cursor is now working as expected.
Still no notice about any new updates though, about shows same version data.
I’m not really sure why a pending osx update would interfere with cursor’s comms, but it was either that or otherwise a reboot was needed (which again is strange behavior for OS X - par for the course on windoze).
Either way problem solved, maybe it helps someone else in future.