Fatal Install Error

We so need this plugin. I was crushed to see this error when we installed it.
What to do?

Fatal error: Uncaught Error: Class ‘Sujin\Plugin\PluginMgr\Bootstrap’ not found in /var/www/cit_/wp-content/plugins/plugin-grouper/plugin-grouper.php:51 Stack trace: #0 /var/www/cit_/wp-admin/includes/plugin.php(1897): include() #1 /var/www/cit_/wp-admin/plugins.php(178): plugin_sandbox_scrape(‘plugin-grouper/…’) #2 {main} thrown in /var/www/cit_/wp-content/plugins/plugin-grouper/plugin-grouper.php on line 51