I could not activate my redeem code.

Either go do what the prompt advises you or go back to the store you bought the card from and have it activated by the person at the cash register. However you most likely will need the receipt for that. Happened to me a couple times before, because it seems that those cards get sold so seldomly at some stores that the person who is supposed to active it when you are buying it, forgets to do it or doesn't even know that they have to.