Payment field: Allow Check out when cart is $0 ?

I have items that people can apply a coupon which makes their total $0.00 but currently I get an error if this coupon is applied.

Please allow me some time to check the issue further and I'll get back to you as soon as possible.

Upon checking further, I'm afraid it is not possible to submit a form with the PayPal Checkout payment field if it has 0 (zero) on its total amount.

How would you like to consider creating the products you listed in the payment field outside the payment field using basic form fields instead. We can also try having the Coupon field created outside the payment field, too. In this case, the form will only pass a total value to the PayPal Checkout payment field if it is not zero (when a valid coupon code is entered). Otherwise, if the total amount is zero after providing a valid coupon code, the PayPal Checkout field will be hidden, no payments will be processed, but your respondents will still be able to submit your form.

Thank you for the help... I was able to make a work around where (like you suggested) the Coupon Code was outside the payment box, then set up "conditions" for what people saw based on having that code or not. So now people with what is essential a full refund code ($0), now make a simple selection from a drop down and have a plain "submit" button.  Thank you for the quick response!!