I have tried adding my payment method but it doesn’t go through why??

If you update your payment method or add funds to your Apple ID balance, It would take about 1 to 3 business days in order to process.

See -> Change, add or remove Apple ID payment methods

Change, add or remove Apple ID payment methods – Apple Support (UK)

• Add first the new card, then remove the old one.

Or -> Add money to your Apple ID balance

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

Check again after a few days, see -> Check your Apple ID balance

Check your Apple ID balance – Apple Support (UK) 

See also ⤵️

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

About billing for Apple subscriptions and media products in India

About billing for Apple subscriptions and media products in India - Apple Support

India

•               Apple ID balance (from adding funds)

•               Net Banking (adding funds only)

•               UPI (adding funds only)

If you can't add a card to Apple Wallet to use with Apple Pay

If you can't add a card to Apple Wallet to use with Apple Pay - Apple Support

Change or remove the payment cards that you use with Apple Pay

Change or remove the payment cards that you use with Apple Pay - Apple Support

If you're still unable to update your payment method, Contact Apple Support.

What happens when you try to add the payment method?? Error message(s)? More information would help.