Hello,
Please note we are not saying that the PHP COM extension isn't installed but that some missing permision or connection set up is missing when doing the conversion using MS Word. As you are getting a generic error, we don't know where the issue may come from.
As you are using the conversion plugin based on MS Word, after you have tested that MS Word is installed in your server and can run correctly, we recommend you to test the PHP COM Extension standalone with the most simple sample available on the PHP documentation pages (https://www.php.net/manual/en/book.com.php) and test it using PHP CLI mode (instead of Apache or the web server you are using):
$ php test.php
to check if there's some permission error or missing setup in the web server that blocks PHP to call MS Word through PHP COM. Generating DOCX is done only with PHP, but the conversion plugin based on MS Word uses PHP with PHP COM and MS Word, so the permissions to be applied may not be the same.
Regards.