Snapshot pro installation

This pertains to most of my sites not just 32pearls.com. I usually get error messages when installing Snapshot pro. For the sites it does intall on, it doesn’t work. Most of the time, I get this message:

Fatal error: Uncaught Error: Class ‘Snapshot_Model_Full_Backup’ not found in /web/wp/wp-content/plugins/snapshot/lib/Snapshot/Controller/Full.php:29 Stack trace: #0 /web/wp/wp-content/plugins/snapshot/lib/Snapshot/Controller/Full/Cron.php(28): Snapshot_Controller_Full->__construct() #1 /web/wp/wp-content/plugins/snapshot/lib/Snapshot/Controller/Full/Cron.php(39): Snapshot_Controller_Full_Cron->__construct() #2 /web/wp/wp-content/plugins/snapshot/snapshot.php(234): Snapshot_Controller_Full_Cron::get() #3 /web/wp/wp-content/plugins/snapshot/snapshot.php(8655): WPMUDEVSnapshot->__construct() #4 /web/wp/wp-content/plugins/snapshot/snapshot.php(8759): WPMUDEVSnapshot::instance() #5 /web/wp/wp-admin/includes/plugin.php(2141): include(‘/web/wp/wp-cont…’:wink: #6 /web/wp/wp-admin/plugins.php(175): plugin_sandbox_scrape(‘snapshot/snapsh…’:wink: #7 {main} thrown in /web/wp/wp-content/plugins/snapshot/lib/Snapshot/Controller/Full.php on line 29

Internal PHP error