Hello,
The current stable version of phpdocx doesn't allow applying styles to MathML tags when importing HTML:
https://www.phpdocx.com/htmlapi-documentation/html-extended/insert-mathml-Word-document-with-HTML
This tag doesn't include additional attributes or styles.
DOCXCustomizer or DOCXPath should be used using the current stable release of phpdocx.
Your username doesn't have any license tied, please send to contact[at]phpdocx.com the username or email of the phpdocx account that purchased the license.
Regards.