This could be caused by the Dimensions (other other application) application being minimised or displayed on an external monitor.
To restore the application window to the main screen, try the following:
Click on the Dimensions (or relevant application) application icon in the Windows taskbar
Press Shift+Ctrl+Right click
Then from the pop-up window, select Move, Restore or Maximize [if you select Move you will need to use the arrow keys to move the window]
Other options to try are as follows:
Click on the Dimensions (or relevant application) icon in the task bar and then press Shift+Win+Left arrow or Shift+Win+Right arrow to move the application window between monitors
Click on the Dimensions icon in the task bar and then press Win+Up arrow or Win+Down arrow to resize the application window
Right click on Desktop and select Refresh
Press Win+M to minimise all application windows and then Win+Shift+M to maximise all windows.
OR
To end Dimensions please go to your task manager and end the session.
Log back in to Dimensions, you may be greeted with a message about the system crash. Press yes to continue to log in.