Hello,
Please send to contact[at]phpdocx.com the username or e-mail of the user that purchased the license, and a sample of the DOCX and PDF documents so we can check them.
Also please note that PHP 7.4 is supported since the release of phpdocx 9.5 (https://www.phpdocx.com/news/post/phpdocx-v9-5-release-notes/219), so you may find some incompatibilities using PHP 7.4 and phpdocx 6.5.
Regards.