Error when accepting a calendar invite on Thunderbird

Steps to reproduce

  1. Receive a calendar invitation
  2. Click on accept
  3. Error happens: “Processing message failed. Status: 80004005.”

Expected behaviour

The event should be added to the calendar and the answer sent to the organizer

Actual behaviour

I’m experiencing this on Mozilla Thunderbird 68.2.2. This problem happens when I receive an invitation. Sometimes, I see the HTML message (with the Nextcloud logo… see example below). In this case, the error message 80004005 appears.

The event can be accepted only if I manually sync the calendar before. Step to reproduce:

  1. Receive the email: it is shown as an HTML page, with the Nextcloud button “Accept” in the middle
  2. Click on “Accept” (not the Nextcloud button in the middle, but the Thunderbird button, top right)
  3. Error message 80004005 appears
  4. Sync Calendars in Thunderbird
  5. Go back to the message: it is shown as the table mentioned above
  6. Click on the “Accept” Thunderbird button → it works

It should work in step 2 above, I shouldn’t be required to go up to step 6

It happens if the person sending the invite is using Thunderbird, and is using a calendar on the same Nextcloud server. And it can also happen if the sender is not in my organisation. (using Outlook or Thunderbird, I don’t know)

To give you more detail:

  • Here is what I call the “HTML page”: clicking on the Accept button (circled red) doesn’t work (error message 80004005):

  • And this is how it looks like after a manual sync (here, clicking on the Accept button (circled red) works).

It might be related to the server managed scheduling mode: (on thunderbird, I have calendar.caldav.sched.enabled = false

In my config.php, I see:
‘app_install_overwrite’ =>
array (
0 => ‘calendar’,

Should I remove that?

I see related issues here:

Server configuration

  • PHP 7.3.11-1+0~20191026.48+debian10~1.gbpf71ca0 (cli) (built: Oct 26 2019 14:20:37) ( NTS )
  • mariadb Ver 15.1 Distrib 10.3.17-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2
  • Nextcloud 16.0.6


I think this log could be related:
Sabre\DAV\Exception\BadRequest: Calendar object with uid already exists in this calendar collection.

/var/www/html/nextcloud/3rdparty/sabre/dav/lib/CalDAV/Calendar.php - line 201:

OCA\DAV\CalDAV\CalDavBackend->createCalendarObject("27", "d8hifi2s08t ... s", "BEGIN:VCALE ... n")

/var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 1096:

Sabre\CalDAV\Calendar->createFile("d8hifi2s08t ... s", "BEGIN:VCALE ... n")

/var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php - line 525:

Sabre\DAV\Server->createFile("calendars/e ... s", "BEGIN:VCALE ... n", null)


Sabre\DAV\CorePlugin->httpPut(Sabre\HTTP\R ... "}, Sabre\HTTP\Response {})

/var/www/html/nextcloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105:

call_user_func_array([ Sabre\DAV\ ... "], [ Sabre\HTTP ... }])

/var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 479:

Sabre\Event\EventEmitter->emit("method:PUT", [ Sabre\HTTP ... }])

/var/www/html/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254:

Sabre\DAV\Server->invokeMethod(Sabre\HTTP\R ... "}, Sabre\HTTP\Response {})

/var/www/html/nextcloud/apps/dav/lib/Server.php - line 316:


/var/www/html/nextcloud/apps/dav/appinfo/v2/remote.php - line 35:


/var/www/html/nextcloud/remote.php - line 163:

require_once("/var/www/ht ... p")

Does nobody meet the same issue? I don’t see any answer neither here nor on :cry::cry:

For the record, the solution is to let Thunderbird manage the invitations:

  • Go to your calendar on Thunderbird
  • Right-click on your calendar name (on the left of the window)
  • Choose Properties
  • Check the box Prefer client-side email scheduling
  • Click OK