My 2 Day Free Xbox Live Gold Passes won't work?

I just ran out of Gold Xbox Live Membership, and I found three 2 day gold passes for me to use. I went to the dashboard, and it said i ran out of gold, i clicked on renew membership, selected redeem code, entered my code (I made sure I made no errors), and when I selected "done", it says "this code isn't valid. Please enter a valid code". I tried 2 of my passes, and neither work. How do I fix this? Could it be that the passes expired? Thanks