Some Zeevex users have reported a problem when they bought multiple cards at once, but only one of them redeemed successfully.  The others were rejected as inactive.

The problem is that at the register, instead of scanning each card individually, the clerk scanned one card multiple times.  This will not work because each card is unique and must be scanned individually to be activated.

If this happens to you, the easiest solution is to take your cards and receipt back to the store, explain what is said here, and have them refund you the money for the cards that were rung up improperly. Then immediately buy them back and have the clerk scan each one individually this time.