That is a weird problem. It's possible it could be a problem with your league client, but I doubt that. You could try repairing it to solve the issue. You can do that by opening League of Legends, and before pressing the PLAY button, go to the top right corner and click the gear, press "repair." However, I think it would be best to contact Riot Support by clicking this link. They will be able to make sure it is attached to your account properly.