All CD keys are single-use and become invalid after redemption, along with the trade offer being sent.
Simply click the blue "i" icon next to the input field, and it will take you directly to your Steam profile where your trade URL is located below the "Third-Party Sites" tab.
This error code indicates that your CD key is either invalid or has already been redeemed.
This error means that either Steam or our web host is experiencing issues and is unable to redeem your key at this moment. Please give it some time and try again later.
If you see this message, it means that you are trying to redeem more TF2 keys than we currently have in stock. Please wait until keys are restocked or contact customer support via live chat in the lower right corner of your screen.
The most common reason for this error is you being unable to accept trade offers. Please make sure that:
And then try redeeming your key again. However, Steam itself could also be having stability issues, so just give it another try a bit later.
If you see this message, it means that your key has been redeemed successfully, and your keys have been sent to you. Allow up to 30 seconds for it to arrive.