Hello,
That error appears when phpdocx can't open the DOCX file to be used as template, can't read the base template available in the templates folder of the package or it isn't a valid DOCX file (a DOCX is a ZIP file). Please check the path you are using is correct and PHP has read access, you have copied all phpdocx files and PHP can read them, and the DOCX is correct and valid.
We also recommend you check and run the sample included in the package (examples folder) using the PHP CLI mode. phpdocx 14 is compatible with all PHP versions from PHP 5.6 to PHP 8.2.
Regards.