Seeing "Unable to download Visualforce page {(!string.IsNullOrWhiteSpace(ex.Message) ? $": {ex.Message}" : ". ")} (ResourceInvalid)" error message when running a DocGen Package.

The issue will occur if you're trying to render a PDF from a Visualforce page but the Visualforce page may contain an error (possibly in the Apex controller or extension) or the Visualforce page is using components not designed for rendering PDFs.

Please see additional information regarding this error at: https://help.nintex.com/en-us/docgen/docservices/Default.htm#cshid=9083