Welcome Mariasmendes,
Thank you for using Apple Support Communities. Based on your post, you're unable to use your Apple ID balance to pay for your iCloud storage. We'll do our best to assist with this.
It sounds like you're unable to select the Apple ID balance as the payment method, even though you can see the balance.
We'd first confirm, that the balance exceeds the amount going to be charged for your iCloud storage.
If you haven't yet, we'd close the app using steps in: Close an app on your iPhone or iPod touch
Then Restart your iOS device normally.
If needed, make sure any added payment methods do not require information to proceed in Settings > [Your Name] > Payment & Shipping.
Should the issue continue to occur, then it would be best to connect with Apple Support directly: Get Support
Wishing you well, take care.