Debit card payment method was declined in app store. How do I purchase?

Apple doesn't usually accept debit cards, in general. Especially if it is a prepaid debit card that you purchase in a local store.

Is this debit card issued by your bank in which you have an account to which the card is tied?

ASC - Late 2012 Mac mini, macOS 10.12.4;  Watch, 38 mm silver AL, watchOS 3.1; iPad Air 2 & iPhone 7+, iOS 10.3.1; TV 4th Gen,  Airport Express

Hello pmmanuel2001,

This is the part of the link I gave you that should be checked out, in particular the information on your account information page.

'You might be able to use other payment types in your country or region. You can see all accepted payment methods on your Account Information page in iTunes.

To automatically open iTunes and sign in to your Account Information page from your computer, click View My Account. Or follow these steps'

Because your card says Visa or Mastercard that is not a guarantee a payment would be made. A debit card always requires funds (whether money or agreed overdraft) to be available at the time of presentation.

The issue with a bank issued debit card is that the system will run a check of the card for a small transaction. If that transaction is declined by the bank for lack of funds or any other reason, then the payment method is determined to be unacceptable and declined as a payment method for your account.

Do they sell iTunes Gift Cards in local stores in India? If so, buying them and redeeming them so that you have credit on your account will also allow you to buy apps from the Mac App Store. The Apple content stores; iTunes, iBooks, Music, Video, Mac Apps, etc. all use the same account. Credit for iTunes is credit for the Mac App Store.

Take a look at this article If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store - Apple Sup…

Credit Card.