My Apple Card has balance but can’t be used or redeem

Do you mean an Apple credit card, or do you mean an Apple Gift Card?

Your description is confusing. Credit cards do not have balance, but then gift card can have balance but you cannot see what it is. Credit cards cannot be redeemed, but gift cards can be.

Read this support article to learn how to redeem your Apple Gift Card or App Store & iTunes gift card --> How to redeem your Apple Gift Card, App Store Card, or App Store & iTunes Gift Card - Apple Support

If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card read this document about things to try --> If you can't redeem your Apple Gift Card, App Store Card, or App Store & iTunes Gift Card - Apple Support

Refer to the second link I provided. You haven't told us what makes you think it cannot be redeemed. Usually there's a message that will match one in the support article and tell you what to do.