Xcode can't open because it is updating

I have a mac-mini (late 2014) running Monterey 12.3.1.

Since 12.3.1 installed (a couple of weeks ago) I haven't been able to open Xcode. The message "You can't open the application 'Xcode' because it is being updated." appears.

I've shutdown the machine down and restarted it - no change.

Gone to the App store and tried to download Xcode again. It never completes. Just the line circling for hours.

Is it time upgrade my machine?