i cant buy tiktok coins through my itunes balance

hello, I'm trying to purchase coins in TikTok by paying from my App Store/iTunes balance, which has $7 on it from a gift card, as I don't have a bank card or PayPal. i'm trying to make the payment, confirming with Face ID, and I'm getting an error: Your purchase can't be completed, please contact iTunes support for assistance. The next error message is "Payment processing error. Provide the necessary information, make the payment in the App Store, and check your Coins balance in 3 minutes." What should I do? Why isn't the payment working? I really need these coins. What's the problem? The song was successfully paid for in the iTunes Store, but there was an error in TikTok. Please help me resolve this issue.🙏🙏🙏