What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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You did not tell what was the error exactly was..
BUT I made a test submission using your jotform http://www.jotform.us/form/42657063845158
and I was able to see this error screen in the Paypal payment screen.
Was this the error you were referring to? If it is not, please provide us more details what exactly was the error.
If it is, then I suggest you redo the paypal integration by following the user guide strictly.
Make sure that in the Account Information in the integration wizard, you provide the correct paypal email account.
After completing the integration check by submitting the jotform again.
Inform us if issue remains and not resolve by following the suggestion.