CAN'T DOWN LODE ANY GAMES I PAYED FOR

i GOT Command & Conquer, The ultimate Collection. I input  the code and now no way to down lode anything. tryed a 2nd time the system say the code has been used now. whats the deal did I get rip off. I paid money for a code that does not work at a web site that will not even show me my games. and no way to find them. What am I to think.