Are you using the Pro version? If not then I don’t think that it will work with ACF fields. I am not familiar with the WP All Export, but I do use WP All Import and ACF fields requires a premium add on.
If you are then you should contact support for that plugin http://www.wpallimport.com/support/ or you should ask on the support forum for the plugin in the WP repo https://wordpress.org/support/plugin/wp-all-export.
