This could be a simple error related to the window size. However the mouse on one of the corners until the resizing icon appears, then keep the button press and drag the icon until it reaches the desired size. In most cases, you can simply double click that window and the software will go into fullscreen, then double click it again and normal window mode should be provided.
Additionally, reinstall the software or Repair it using its own installer from Uninstall a program in Control Panel.