Gangplank & Skins are Unavailable

I tried to buy Gangplank so I could get his free skin ( mentioned at http://na.leagueoflegends.com/en/news/game-updates/special-event/gangplank-returns-and-event-end-draws-near ) but he doesn't appear in the shop at all. http://imgur.com/sfQVB3n

If you go to Available Champions ( because he's currently free ) you can click him, but everything says Unavailable. http://imgur.com/RZRx1bV

Anyone know anything about this?