You don’t have permission to access error

Hello, after I enable the plugin I get this error to my pages,
You don’t have permission to access /wp-content/cache/all/…./index.html on this server. Permissions are set to 755 and owner is the same to all of the folders (as shown here https://www.wpfastestcache.com/warnings/delete-cache-problem-related-to-permission/). I even created a new htaccess just in case it had any conflict with my settings but still the error remains. Any ideas to resolve this problem? Thank you in advance.