Every time I try to log in to minecraft, it will try to log in but then about 30 seconds later say "Login failed". Just "Login failed", not "account not premium" or "can't connect to minecraft.net". I can still log in to minecraft.net and mojang.com fine, but the launcher fails to log in. Some additional information is that when I log in to both mojang.com and minecraft.net it tells me I have not bought the game, although I clearly remember entering a code off a prepaid card I bought from Gamestop.
Any and all help is appreciated, thanks.