The on-screen keyboard is a temporary solution. If the computer is in warranty, I suggest you contact Sony to check it out. If you think you know what you are doing, try taking off the top of the keys and see if there is something in the way of the contact.
Picture guide for taking out and putting back keys
Also, try pressing the key without the top. If it still doesn't work, definitely have some licensed shop see it.
-------
Trolling is a art.