When I render a PDF that is a dynamic XFA form, I see an error message: "Warning: This form is not supported with the current version of Acrobat or Acrobat Reader"

You see this message when rendering or printing the PDF because of the PDF content for that page. The PDF Library is rendering the pages as they're designed. This document has gone through a workflow where the PDF form content has been removed and replaced with the message you are seeing.

These documents are encountered under a limited set of circumstances. First, it must be a dynamic PDF Form and then processed by LiveCycle server for enabling features. If it is processed by LiveCycle, when Adobe Acrobat or Reader seeks to render that PDF Form for display, it will use the dynamic XFA rendering functionality and will not update the PDF structures behind the form. Instead, Reader adds the warning message as the default PDF content.

The PDF Library does not have access to the XFA rendering mechanism used in Acrobat and Reader and cannot render the form as intended.