I created new account with Owncloud server (10.5.0 stable).
I tried:
https://server/ (I have /.well-known/caldav and …/carddav URLs).
https://server/remote.php/dav
https://server/remote.php/dav/principals/users
https://server/remote.php/dav/principals/users/USERNAME
https://server/remote.php/dav/calendars/USERNAME/personal
I can see http access from eM Client on Owncloud server (access.log).
But eM Client have errors (no method, no folders, …).
Another CalDAV clients (DAVx on Android, Evolution on Linux) work fine.