Fatal error: Uncaught Error: Class "Sabre\DAVACL\AbstractPrincipalCollection" not found in D:\xampp\htdocs\pimcore\my-project\vendor\sabre\dav\lib\CalDAV\CalendarRoot.php:22 Stack trace: #0 {main} thrown in D:\xampp\htdocs\pimcore\my-project\vendor\sabre\dav\lib\CalDAV\CalendarRoot.php on line 22