Not able to test Paypal form submission when using seller email account as the buyer account also

From PREVIEW I submit a request for an event registration (product) Paypal returns and error in the "seller email".  The seller email is the same as the email used for the Paypal account.

Where do we look to resolve this?

You can do the test payment after enabling Sandbox Mode in the Paypal payment.

Check the image below on how to.

You can also refer to the same discussion thread here 

https://www.jotform.com/answers/730955-How-to-test-Paypal-payment-form#1

Let us know if you need further assistance.