Directly making API calls to generate a source_id isn’t supported. You’ll have to use our generated iframe to generate the tokenized card that you pass to CreatePayment.
Have you taken a look at the React Web Payments SDK from our partner? 
Directly making API calls to generate a source_id isn’t supported. You’ll have to use our generated iframe to generate the tokenized card that you pass to CreatePayment.
Have you taken a look at the React Web Payments SDK from our partner?