App Store difficulty

I know that some people are able to download free (and only free) apps with no payment method but there are multiple scenarios where Apple will require a payment method such as a credit or debit card be present in order to download anything from the Stores. The payment method may not be charged if you also have account balance, but the payment method has to be present. Since it appears you are encountering one of those situations, you have no option but to enter a valid payment method if you wish to continue downloading. Read the support article Add a payment method to your Apple ID - Apple Support about how to do that. This next article lists valid payment methods for different countries but note that in this case Apple Account balance alone apparently does not meet the requirement Payment methods that you can use with your Apple ID - Apple Support