Fontawesome error

I see an error in frontend editor of visual composer fetched form maxbutton:

Refused to apply style from ‘https://domain.com/wp-content/plugins/maxbuttons/assets/libraries/font-awesome/css/font-awesome.min.css?wp-mce-4800-20180716’ because its MIME type (‘text/html’) is not a supported stylesheet MIME type, and strict MIME checking is enabled. If you try to go to the url the file is 404. Tried on staging to extract the plugin in file manager to reupload all files without success solving the issue.