The "CTRL" key on the left side of my laptop won't work with keyboard shortcuts such as Ctrl+V, Ctrl+C, Ctrl+Z. It also does not function while using Firefox. I can't use keyboard shortcuts to do things like switching tabs (Ctrl+Tab), closing tabs (Ctrl+W), or opening new tabs (Ctrl+T). Strangely, the Ctrl key on the right side works properly. What has happened to my laptop's keyboard? How can I restore function to the left Ctrl key/?