I've been trying to get Unchained Alistar for a few weeks now through the Youtube promotion and it always says something like "there was an error adding the skin to your account". Is anyone having the same problem, did they end the promotion, or do I have to own Alistar to get it?
Me too, been trying for over a month now, it just doesn't work... :(
I had to message Riot support and they gave me the skin and champ the next day.
Submit a ticket (send a message) to Riot, explaining your issue. Include a snapshot proving you subbed to the YouTube channel, and they should happily give you it.
In the meantime, have you gotten Riot Girl Tristana and Dreadknight Garen from their Facebook and Twitter?
