I can’t buy gift cards with my chase debit card, linked to my wallet

I can’t buy gift cards with my chase debit card,

Apple Gift Card or App Store & iTunes gift card -> where to buy:

Actually, you can buy an Apple gift card at many places, it depends of course on where you live.

At an Apple Store or an Apple Authorized Reseller in your region certainly, but also at a good bookstore, supermarket and/or drugstore.

See this Apple article: How to redeem your Apple Gift Card or App Store & iTunes gift card

How to redeem your Apple Gift Card or App Store & iTunes gift card – Apple Support (UK)

Then see the following Apple articles: 

Add money to your Apple ID balance

Add money to your Apple ID balance - Apple Support (IN)

What you can buy with your Apple Gift Card or Apple ID balance

What you can buy with your Apple Gift Card or Apple ID balance – Apple Support (UK)

I got declined when ever I wants to buy something from Apple Store

See -> If your payment method is declined in the App Store or iTunes Store

If your payment method is declined in the App Store or iTunes Store - Apple Support

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Get more help

• If you disputed a charge from the App Store or iTunes Store, contact your financial institution again to authorize that charge and future purchases from the App Store or iTunes Store.
• If you're outside of the United States, you might need to contact your financial institution to allow international purchases.
• In some countries and regions, your payment method might be declined because of changes to local law. Learn about billing and purchases in Europe or what to do if your card is declined in India.
• If you still need help, contact Apple Support.