App Store is not accepting my payment method

You need to update / edit your payment information.

👉 Sign in to your Apple ID account page and edit your Apple ID details.

https://appleid.apple.com

On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.

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

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

Or use another payment method:

Add money to your Apple ID balance

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

You need a valid credit card issued by a bank in the country the store is in and you need a billing address in that country.