Hello,
If you create an empty document from scratch, the DOCX output will always be 'corrupted'. You need to add at least one content, use a template or change the default base template from phpdocx.
About your issue, it seems your server is returning a wrong DOCX when downloading it. Maybe your web server has a wrong config to return DOCX mime types. We recommend you to run the included examples and download the DOCX output using an alternative such as FTP just as test; the library is working perfectly.
Regards.