Why can’t I use my iTunes card

Read again -> Related Article -> How to redeem your Apple Gift Card or App Store & iTunes gift card

See also -> If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card

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

• You can't redeem Apple Gift Cards or App Store & iTunes Gift Cards outside the country or region of purchase. For example, if you bought an App Store & iTunes Gift Card in France, you can't redeem it in the App Store in the United States.

See also -> About Gift Card Scams

https://support.apple.com/gift-card-scams