Cant purchase with appstore balance

Cant buy things with apple balance

Do you get any error message?

See the following Apple articles:

Change, add or remove Apple ID payment methods

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

Payment methods you can use with your Apple ID

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

You can add your Apple ID balance as payment method:

Add money to your Apple ID balance

Add money to your Apple ID balance – Apple Support (UK)

Check your Apple ID balance

Check your Apple ID balance – Apple Support (UK)

👉 If you still need help, contact Apple Support.