Apple ID balance available, during purchases verification is needed with credit card

Is 60 euros enough to cover the purchase price plus any applicable taxes? Is the in app purchase a subscription? If the answer is yes to either of those, a credit card is required.

You can contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide   -

Apple Support schedule phone call     -

Billings and Subscriptions   -

Apple on Twitter

If it has a subscription, you have to have a credit card on file. You can avoid making charges to the credit card if you buy/redeem Apple Gift cards to the account to cover the cost of the subscription. Charges will be deducted from the account balance before your parent's credit card is charged.

Apple Card  -

Gift cards redeem.   *

Gift Card - can’t redeem.   *

App Store & iTunes Gifts - Resend *

Or if you aren't in Family Sharing.

Apple ID - Add funds to your ID      *

So I had gotten a 20 dollar apple gift card, but I tried making a purchase on one app but it said verification needed. But instead of making me use my Apple ID password, it sends me to App Store and showed me needing to use credit cards.