one note not responding in some projects

Cubase 8.5, Windows 10

I have recently been working on a new project, no problems. Suddenly one particular note can no longer be heard if it’s input via a controller or Key Edit keyboard. However If I draw in the note I can hear it fine. I then created a new project from this one and I get the same problem.

I’ve since opened another, but slightly older project to see if there’s the same problem, but no everything’s fine with that one.

Any ideas why I’m suddenly having this problem please?

Add a midi monitor and see if its the keyboard.

Thanks, I’ve not used a midi monitor before…

In my other Cubase projects I can still play and hear this note using my Korg keyboard (or alternatively) by using the mouse on the Key Editor’s keyboard. So the keyboards(s) are definitely still working in those projects.

But in the latest project when I use the Korg keyboard there is now only input activity, similarly if I use the mouse to play the note on the Key Editor’s keyboard the “piano key” is highlighted but there is no longer any sound.

It seems that something has somehow changed within this particular project’s set up, but I’m not sure what, or why.