Why it says my voucher code has already been redeemed?

Your activation code cannot be redeemed under the following circumstances: 
1. The activation code has been redeemed: An activation code can only be redeemed once. If you have already entered the code, please check whether the membership has taken effect in the correct account;
2. The activation code is expired: If your activation code is expired, it cannot be redeemed. It is recommended that you contact the provider of the activation code for further information.