Why does HTML2PDF on CentOS gives "Conversion failed. HTTP Code: 0" errors?

I downloaded trial version of HTML2PDF for Linux(CentOS), unzipped it and placed it in PDFNetC64/Lib directory as specified.

I have downloaded them from
https://www.pdftron.com/pdfnet/downloads.html

I am trying to execute example 4 specified in below link on Linux and it fails but it works perfectly fine on windows.
https://www.pdftron.com/pdfnet/samplecode/HTML2PDFTest.java.html

ERROR LOG:

converter.getLog() gives following error log.

Conversion failed. HTTP Code: 0
You need to specify atleast one input file, and exactly one output file
Use - for stdin or stdout

Name:
  wkhtmltopdf 0.10.0 rc2

Synopsis:
  wkhtmltopdf [GLOBAL OPTION]... [OBJECT]... <output file>

....................................................

Missing output file /tmp/Trn-13276-1466070590-6a3cf462-3860-457e-a657-d6cda0893c9c

Can anyone provide help on this??

Old question but in case anyone else comes across it… for me I got this error (on Ubuntu 16.04) because the html2pdf.so library needed have execute permissions.