After you redeem a card the balance is not updated right away in iTunes: this is a bug/issue with Apple systems. Nothing that iRedeemer / jeTap can fix sadly.

Please follow the instructions shown at:
support.apple.com/en-us/HT202359

iRedeemer is an helper application which help you enter quickly the redemption code. The redemption process itself is done inside the iTunes Application and thus only Apple can tell you if there was a problem redeeming the card.

If you did not see any error while redeeming the code from within iTunes then most likely you are experiencing the issue shown in the link above.