Fatal error: Uncaught Error: Class "Sabre\DAV\Collection" not found in /var/www/illumine/vendor/sabre/dav/lib/CalDAV/Subscriptions/Subscription.php:21 Stack trace: #0 {main} thrown in /var/www/illumine/vendor/sabre/dav/lib/CalDAV/Subscriptions/Subscription.php on line 21