My Apple Gift Card says Not Valid

See this Apple article:  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

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Card is not valid

Card has already been redeemed

Card is not activated

Code is unreadable

Code must be redeemed in a different country or region

Contact Apple Support -> Contact Apple Support.

Beware of -> About Gift Card Scams -> About Gift Card Scams - Official Apple Support 

Where did you purchase that card?

Ask your money back.

That's an expensive lesson.

You can report to the police, you certainly have proof of payment.

If you want to buy a physical Apple gift card, buy at an Apple Store or an Apple Authorized Reseller in your region.

If you have a valid payment method on file, instead of buying or order an App Store & iTunes gift card, you can Add money to your Apple Account balance anytime, no gift card needed, see -> Apple Gift Card - Apple (UK)