This is my configuration for testing…
caldavio:openhab_tasks:url=https://www.google.com/calendar/dav/email@gmail.com/events
caldavio:openhab_tasks:username=email@gmail.com
caldavio:openhab_tasks:password=passwort
caldavio:openhab_tasks:reloadInterval=10
caldavio:openhab_tasks:preloadTime=20000