Greetings Michael,
Thanks for visiting the Apple Support Communities! It seems you're unable to make a payment with Apple Pay, as you mentioned your Apple Pay Cash account isn't being funded from your credit cards as expected.
To add money to your Apple Pay Cash account, the money would need to be funded from a debit card or a prepaid card, as outlined within the following guide: Add money to Apple Pay Cash
You can read additional information for making person to person payments with Apple Pay Cash from the following support article: Set up Apple Pay Cash and person to person payments
You can read information for using Apple Pay to make payments in stores, on the web, in apps, and more, from the following guide: Using Apple Pay in stores, within apps, and on the web
Cheers.