i have this output error: Warning:

Hi i have this output error:

Warning: require_once(/home/user/public_html/wp-admin/network): failed to open stream: Success in /home/user/public_html/wp-content/plugins/marketpress/includes/addons/class-mp-addons.php on line 81

Fatal error: require_once(): Failed opening required '' (include_path='.:disappointed:usr/lib/php:disappointed:usr/local/lib/php') in /home/user/public_html/wp-content/plugins/marketpress/includes/addons/class-mp-addons.php on line 81

When i have the marketpress and the pro sites on.