Hugh,
Did you change the monitor configuration recently? If you went from 2 monitors to 1 for instance, it might put the application where the second screen used to be (off screen)
Let’s try this. Close Spike and delete the file at this location.
C:\Users\YourUserName\AppData\Roaming\SignalHound\Layout.ini
Once deleted, restart Spike.
If you don’t see the AppData folder at first, it is a hidden folder, you will have to “Show hidden folders” in the file explorer settings menu.
Let me know if this resolves the problem.
Andrew