Your document root is:
/var/www/vhosts/domain.com/httpdocs
And your <Directory>
container is for:
/var/www/vhosts/domain.com/vhosts/
Are those supposed to be different? If your htaccess file is in the httpdocs
directory, then that directory doesn't have the AllowOverride All
associated with it. If your htaccess file is in the vhosts
directory, then it's not being accessed when you go to your website.