Form says that the payment field is required though everything is filled

It has worked fine previously but now gives an error regarding required field validation. A customer called and said they could not register for a class because the form gave them an error regarding their payment information. They said that despite filling in the information on the form in all fields it still tells them that the field is required. I went to test the page and experimented. I was able to replicate the error if I let the browser perform an "auto-fill" of the data in the fields. I asked the customer to try manually entering all of the fields and they are still receiving the same error.

This was not an issue in the past. My customers need to be able to register for classes.

PLEASE HELP!!

I see that there is an incorrect formula in the Custom Donation calculation field which is causing the issue. It looks like the fields related to this calculation are removed from the form.

Since the calculation is done using the conditions based on the number of participants, you can remove these fields in the calculation wizard. I have cloned your JotForm to my account and tested after removing these fields which is working at my end. Please remove these fields from the Custom Donation calculation field and let us know if the issue still persists. We will be happy to assist you further.