What should I do if I cannot enter certain characters with my keyboard?

• Check if the Caps Lock indicator light on the Caps Lock key is on or off.
  When the indicator light is on, characters typed will appear in uppercase (or lowercase if you also hold down the Shift key).
  When the indicator light is off, characters typed will appear in lowercase (or uppercase if you also hold down the Shift key).
  Press the Shift+Caps Lock keys to turn the Caps Lock indicator light on or off.