I auto-generated a task form for my BPM test project and got this error while submitting the Initiator user task form.
404 Not Found
Set the init-param debug_mode to “true” to see the complete exception message.
This issue is because of generated ADF task flow. The Unbounded Task Flow references a page that wasn’t generated, Empty1.jspx . This behaviour happens because of adfc-config.xml, located in your InitiatorTask Project [web content > public_html > page flows] folder. If you didnt change it, open it and you will notice that it directs the flow to an Empty1.jspx page.
Create Empty1.jspx. Just Right Click> Create Page
It automatically closes the window once the form is submitted.