How do I delete the Nintex form and just go back to the SharePoint out-of-the-box form? I tried deleted the versions. That didn't work. New Item still popped up the Nintex form. I tried editing the form with InfoPath and then resetting (Form Settings) back to the SharePoint form. That popped up the Nintex form. Do I have to totally rebuild the list?
Sorry to hear that Nintex Forms does not suit your solution.
To go back to a SharePoint form open the form in the Nintex Forms designer.
From the ribbon click Delete Form.
This will take you back to the SharePoint Default form.