Minecraft.net says that I need to buy my game.

Last day I enter to Minecraft´s launcher, I click on Play and I try to join a server but it says: "Failed to login: Invalid Session (Try restarting your game)"

I go to Minecraft.net and I login with my account and when I go to the shop It says that I can buy the game, but a month ago I reedem a Gift Code.

I enter on account.mojang.com and in My games it says: Did you know that if you have an old Premium Minecraft Account you can import it into this account?
If you do, you should start using your Mojang account e-mail as username when logging in to Minecraft.

What happens, I read if your code is refunded you cannot have your account premium anymore (If you dont buy the game), but I don´t received any email.

Thanks.