Why I cannot download app

Based on your country of residence or country you have selected under your Apple ID --> Payment methods that you can use with your Apple ID - Apple ...

Ask your bank only one thing, i.e. if the Debit/Credit card which is issued to you is valid internationally.

Rest everything check at your end.

Check the following

1. The payment method that you are adding is of the same country as that of App Store Country on your iPhone
2. You have valid payment plan / debit / credit card from an authorised bank from the same country as that of your Apple ID
3. Learn more about family purchases and payments.

Know it here --> If your payment method is declined in the App Store or iTunes ...

Check the following

1. The payment method that you are adding is of the same country as that of App Store Country on your iPhone
2. You have valid payment plan / debit / credit card from an authorised bank from the same country
3. Payment methods that you can use with your Apple ID - Apple Support
4. Learn more about family purchases and payments.
5. Please check if your Debit/Credit card is valid internationally