Several Payments were not processed, but the customer still received registration confirmation, yet payment shows $0.00

Is this the form in question http://www.jotform.us/form/73094110384148?

The payment field on this form is not required so they can submit the form normally without making a payment. 

If you want users to pay, make sure to make the field required so they can't submit the form without selecting a product.

No it is this form,
https://form.jotform.com/72964923884170
However, there were 3 payment choices at the time of the issue. Due to
Registration limits, I removed the other two options.
...

Thanks for providing the right form.

So I checked that form and the product field is also not required.

In the last submission of that form, there was no product selected so the form submits without any payment, hence the total is 0.00.