OMG OMG I turned off Apple Cash and it worked - You were right!!! Except in my case, Apple Pay is still on, but Apple Cash is off.
First, I removed my bank account from Apple Cash, and removed PayPal from the payment methods for iTunes, and only left the Apple Credit card in the wallet and iTunes, and then I shut off Apple Cash.
Then I tried to make a purchase in the PoGo shop and it worked!!
I think the bank account definitely has something to do with it, because today my bank literally SHUT OFF my debit card without even asking me if the $1.00 purchase for the PoGo ticket was fraud. They just shut it off. And I got a push notification on my phone that the debit card was no longer available for making purchases. And the debit card was tied to Apple Cash. OMG this Apple payment system is SO MESSED UP.
BUT IT WORKED!!!