so sadly riot expired all the codes almost 1 year ago, if u had codes in that time u had a limited time to used them. That´s dont work anymore .
Taken from Riot Directly
"Riot is taking action against these scammers at the source. We are working with multiple payment processors to inform them of the situation and recommend they no longer process fraudulent payments from these sites. Additionally we will be deactivating all previously issued skin codes starting today. If you have a skin code that you acquired legitimately please send a request to Player Support and include proof of ownership. We’d be happy to help redeem the content to your account, but please note after 07/23/14 we will no longer be redeeming codes for any reason."