That's not a valid URL for anyone but user1.

Permissions: Advanced sharing, all permissions given to All 
Authenticated Users.
So the calendar owner is user1 that was also in the url that I gave to 
the users to put in TB.
The user1 only is used to share calendars he doesn't exist as a 
physical user. So it is the user that the agenda has been shared with 
(all autheniticated users) that has the problem.
But now I see when I log in with my user the caldav url included my 
username instead of the calender owner.
For WebDAV/ICS Subscription URL it is the correct user.
Adding the caldav url with my user seems to work in TB, but it  should 
work with the calendar owner instead

Does this happen for the calendar owner, or for the user that the 
calendar has been shared with? What permissions does the shared user 
have?

This is not a duplicate of that bug. I just upgraded kronolith to 
4.2.7 and the problem stiill exists
This is the error location in lib/Application.php
684             $calendar = $calendar_manager
685                 ->getEntry(Kronolith::ALL_CALENDARS, $id)
686                 ->toHash();

Going to the url in a browser works, then I get a sabredav view with 
the needed .ics files.
But the PROPFIND fails from Thunderbird.

BR,
Maarten

Bug: 13975

Hmm, Thunderbird still isn't able to view the calendar.

The error is on the PROPFIND http call: PHP Fatal error:  Call to a 
member function toHash() on a non-object in 
/var/www/horde/kronolith/lib/Application.php on line 686

Never mind, found the problem.
The calenders were created in an older version of Kronolith.
I did a change on all of them just by clicking save on every calender.
Now they work.

Hi,

Problem occurs when you add additional calendars to a user and share them.

The sharing of the users main calendar works fine.

This is the error I get when I go to the URL:

A fatal error has occurred
Call to a member function toHash() on a non-object

1. Horde_ErrorHandler::catchFatalError()

Details
The full error message is logged in Horde's log file, and is shown 
below only to administrators. Non-administrative users will not see 
error details.

ErrorException Object
(
     [message:protected] => Call to a member function toHash() on a non-object
     [string:Exception:private] =>
     [code:protected] => 0
     [file:protected] => /var/www/horde/kronolith/lib/Application.php
     [line:protected] => 686
     [trace:Exception:private] => Array
         (
             [0] => Array
                 (
                     [function] => catchFatalError
                     [class] => Horde_ErrorHandler
                     [type] => ::
                     [args] => Array
                         (
                         )

                 )

         )

     [previous:Exception:private] =>
     [severity:protected] => 1
     [logged] => 1
)