PayPal Business: I tested a credit card instead of debit card and got this error

The request was refused

I can see that you are using PayPal Business integration. Note that there were certain requirements to use this type of integration. You need to ensure that the Paypal account you're using is of Business Type and that you have already set up a merchant account.

If you haven't setup a business account yet, you may follow this guide https://www.jotform.com/blog/how-to-set-up-a-paypal-business-account/.

Now, if your account is already a business-type, I would suggest removing the payment field, re-add it to the form, then reconnect it with the account. You need not to worry about the created product as it will be carried over to the new payment field.

And after doing so, please try making another test submission again and see if it makes any difference.