If your Shift key not working, there may be something wrong with your keyboard driver. Click Apply when a change is made then try your keyboard again. Go back to Control Panel then look for Region and Language and make sure all tabs at set to the United States. If this doesn't work try checking the keyboard language if set correctly. Uncheck where it says Turn on Sticky Keys and click OK.
Click on Change how your keyboard works. Go to Control Panel then look for Ease of Access
Did you make any software or hardware changes on your PC? Have you tried checking with an external keyboard?