PayPal Pro Integration: some users receive "Invalid Configuration; This transaction cannot be processed"

Hi there! I'm writing because I have a published form that I am using to accept applications to a holiday craft show. The application requires a $20 application fee, so I included a PayPal module in the form so we could accept payment.

https://form.jotform.com/92195499142971

The problem is, even though we have accepted a number of applications with fees, I have received just as much feedback from other applicants who are report seeing an error when they try to submit the form. Most of these users report an error saying "Invalid Configuration; This transaction cannot be processed. The merchant's account cannot accept payments." However, as I mentioned, we have received completed applications along with payments, so something isn't adding up.

If you have any idea of what might be happening to cause the error, or if there is anything I should adjust on my end that might help prevent this error from occurring, please let me know! This is a very important and time-sensitive matter so your prompt response would be appreciated.

Thanks 

The PayPal Pro payment field appears to be correctly integrated. Please contact PayPal support, probably there is something in your PayPal Pro account that needs to be updated.