Your Purchase Could Not Be Completed

Hard to say where to refer your Q from the details you've posed here.

Could be a 'payment method' issue, and if that includes your Apple ID:

• Payment methods that you can use with your Apple ID - Apple Support

• Change, add, or remove Apple ID payment methods - Apple Support

While there's a jungle of partial-related answers to unstated questions,

maybe you need to be more point-on with any question(s) in this area.

Apple Pay, Apple Card, and all these different things, get together at times.

And arrive at various destinations; some separately, others arrive in groups.

Not one of my bookmarked Support links cover all extenuating circumstances.