Support intro
Sorry to hear you’re facing problems 
help.nextcloud.com is for home/non-enterprise users. If you’re running a business, paid support can be accessed via portal.nextcloud.com where we can ensure your business keeps running smoothly.
In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 20.0.5): 27.1.1
Operating system and version (eg, Ubuntu 20.04): Debian 12 (Docker), Host MacOS 14 (Sonoma)
Apache or nginx version (eg, Apache 2.4.25): 2.4.57
PHP version (eg, 7.4): 8.2.11
The issue you are facing:
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
- Add cal/carddav to davx5 via nextcloud app or app password.
- Enable calendars and / or contact lists.
- Attempt to sync
The output of your Nextcloud log in Admin > Logging:
The logging tab says: “No server logs” with all filters enabled.
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
<?php
$CONFIG = array (
'htaccess.RewriteBase' => '/',
'memcache.local' => '\\OC\\Memcache\\APCu',
'apps_paths' =>
array (
0 =>
array (
'path' => '/var/www/html/apps',
'url' => '/apps',
'writable' => false,
),
1 =>
array (
'path' => '/var/www/html/custom_apps',
'url' => '/custom_apps',
'writable' => true,
),
),
'instanceid' => '*',
'passwordsalt' => '*',
'secret' => '*',
'trusted_domains' =>
array (
0 => '192.168.1.12:5676',
1 => '*',
),
'datadirectory' => '/var/www/html/data',
'dbtype' => 'mysql',
'version' => '27.1.1.0',
'overwrite.cli.url' => 'http://192.168.1.12:5676',
'dbname' => 'nextcloud',
'dbhost' => 'db',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'nextcloud',
'dbpassword' => '*',
'installed' => true,
'app_install_overwrite' =>
array (
0 => 'openotp_auth',
1 => 'pdfdraw',
2 => 'talked',
3 => 'holiday_calendars',
),
'updater.secret' => '$*',
The output of your Apache/nginx/system log in /var/log/____: is a docker log OK?
=> Searching for scripts (*.sh) to run, located in the folder: /docker-entrypoint-hooks.d/before-starting
==> but the hook folder "before-starting" is empty, so nothing to do
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.27.0.3. Set the 'ServerName' directive globally to suppress this message
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.27.0.3. Set the 'ServerName' directive globally to suppress this message [Sat Oct 07 07:13:58.111985 2023] [mpm_prefork:notice] [pid 1] AH00163: Apache/2.4.57 (Debian) PHP/8.2.11 configured -- resuming normal operations
[Sat Oct 07 07:13:58.112412 2023] [core:notice] [pid 1] AH00094: Command line: 'apache2 -D FOREGROUND'
192.168.65.1 - lividhen [07/Oct/2023:07:14:01 +0000] "PROPFIND /remote.php/dav/principals/users/lividhen/ HTTP/1.1" 207 2453 "-" "DAVx5/4.3.7-ose (2023/09/22; dav4jvm; okhttp/4.11.0) Android/13"
Apache log is 0 bytes
Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.