iTunes gift card says it's bad

I tried redeeming iTunes card $100 and it shows bad .. what does it means

If you are having problems redeeming a gift card, review the possible reasons and suggestions listed in this support article --> If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support

If your issue is not listed, follow the directions at the end for contacting Apple Support.

Card is not valid --> If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support