Thanks for reaching out to Jotform Support. You should enable Set Custom First Payment Cost to see the field. Can you provide the the Form URL in question so we can check it out? Here's the guide to locate the form URL.
After we hear back from you, we’ll have a better idea of what’s going on and how to help.
lepoulsen
Replied on March 19, 2023 at 12:11 PM
So, after a Chat session, I learned that the custom first payment is only available with Stripe, not Stripe Checkout.