Unable to add my Cash App card as a payment method in the iTunes Store

• And, what message are you getting?
• I assume it is the linked VISA Cash App card?
• Are you able to add it to your Wallet for Apple Pay? Note that you have to verify in the Cash App after adding for approval. Apple Pay is also acceptable for a payment method on your Apple Account.

https://cash.app/help/30810-apple-pay

Generally, that means Apple is rejecting it. This could be something as simple as a fraud alert, prior dispute and even prior declined transactions. Only Apple Support will be able to tell you the exact reason, but it’s unlikely Apple will reverse or even reveal the exact nature of the rejection of the specific payment method.

If you’re in the US please call  1-800-MY-APPLE or outside the US, consult the support articles below.

Contact Apple for support and service - Apple Support

Official Apple Support

Review the payment methods that can be added to your Apple Account based on region here:

Payment methods that you can use with your Apple Account - Apple Support