Please try using PHP CLI mode to check if the document is generated. It seems your server has some problem saving the files, maybe due to some rw access missing or a problem with the temp folder (it can be customized in config/phpdocxconfig.ini).
Also please check the documentation available on https://www.phpdocx.com/documentation/cookbook/download-generated-docx about downloading documents.
We move the post to the board How do I...? and issues, instead of Suggestions.