We see in your script these lines:
use Phpdocx\Transform\TransformDocAdvOpenOffice; $docx = new TransformDocAdvOpenOffice();
This script is not using the conversion plugin based on LibreOffice but the one based on OpenOffice.
As you can read on https://www.phpdocx.com/documentation/conversion-plugin/running-the-first-example-and-available-options, to use LibreOffice you need to use the TransformDocAdvLibreOffice class:
use Phpdocx\Transform\TransformDocAdvLibreOffice; $docx = new TransformDocAdvLibreOffice();
or the transformDocument method to autodetect the conversion plugin automatically from the data of the config file.
After you have set the options in config/phpdocxconfig.ini, please try to run the included sample FormatConversion/transformDocument/sample_1.php using PHP CLI mode:
$ php sample_1.php
It must generate the PDF fine.
If you send to contact[at]phpdocx.com SSH access to your server a member of the dev team can check it directly. We'd need SSH access, the path where phpdocx is installed and an URL to test it using a web browser.