Error loading contacts menu

Nextcloud version (eg, 20.0.5): 21.0.4
Operating system and version (eg, Ubuntu 20.04): Ubuntu 20.10
Apache or nginx version (eg, Apache 2.4.25): Apache 2.4.48
PHP version (eg, 7.4): 7.4.21

The issue you are facing:
When clicking on the contacts menu, it shows that there are no contacts found.
Link to image

Is this the first time you’ve seen this error? (Y/N): Y

The output of your Nextcloud log in Admin > Logging:

{"reqId":"UxJLcIbPfubsZos5sHsB","level":2,"time":"2021-08-15T13:06:44+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"OPTIONS","url":"/remote.php/dav/principals/users/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"lHqtLou3qQO0cDeb9vMz","level":2,"time":"2021-08-15T13:06:44+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"OPTIONS","url":"/remote.php/dav/principals/users/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) remindd/1.0","version":"21.0.4.1"}
{"reqId":"Xx9kTrPAORNStK4pZ9wf","level":2,"time":"2021-08-15T13:06:46+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/principals/users/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"geMF9Joxjzn0CGIkSpCZ","level":2,"time":"2021-08-15T13:06:46+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/principals/users/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"BkAvFkqcvtNjjIXh4uNM","level":2,"time":"2021-08-15T13:06:48+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/calendars/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) remindd/1.0","version":"21.0.4.1"}
{"reqId":"dX5mx6bVz7tjzR8VLmqd","level":2,"time":"2021-08-15T13:06:48+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/addressbooks/users/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"OIRBSSQt4LQuLdpY5Pff","level":2,"time":"2021-08-15T13:06:48+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"OPTIONS","url":"/remote.php/dav/principals/users/Administrator/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"IqGa7v8LPIN2pJVwTwO3","level":2,"time":"2021-08-15T13:06:49+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/calendars/Administrator/app-generated--deck--board-1/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) remindd/1.0","version":"21.0.4.1"}
{"reqId":"ffv1amxguPI6ISIhQCkE","level":2,"time":"2021-08-15T13:06:50+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/addressbooks/users/Administrator/z-app-generated--contactsinteraction--recent/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"79ZCctwBpmatDuUbUOBt","level":2,"time":"2021-08-15T13:06:51+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/addressbooks/users/Administrator/contacts/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}
{"reqId":"hNpWz3F0m4ewl3ycKW12","level":2,"time":"2021-08-15T13:06:53+02:00","remoteAddr":"127.0.0.1","user":"Administrator","app":"suspicious_login","method":"PROPFIND","url":"/remote.php/dav/addressbooks/users/Administrator/contacts/","message":"Could not predict suspiciousness: No models found","userAgent":"iOS/14.7.1 (18G82) dataaccessd/1.0","version":"21.0.4.1"}

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

<?php
$CONFIG = array (
  'instanceid' => 'oc4su7xmhwt4',
  'passwordsalt' => '****',
  'secret' => '***',
  'trusted_domains' => 
  array (
    0 => '****',
    1 => '192.168.1.100',
  ),
  'datadirectory' => '/media/pawel/Seagate/data',
  'dbtype' => 'mysql',
  'version' => '21.0.4.1',
  'overwrite.cli.url' => '****',
  'dbname' => '****',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => '****',
  'dbpassword' => '****',
  'installed' => true,
  'mail_smtpmode' => 'smtp',
  'mail_smtpsecure' => 'tls',
  'mail_sendmailmode' => 'smtp',
  'mail_from_address' => '***',
  'mail_domain' => '****',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtphost' => '****',
  'mail_smtpport' => '587',
  'mail_smtpname' => '****',
  'mail_smtppassword' => '****',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'memcache.distributed' => '\\OC\\Memcache\\Redis',
  'redis' => 
  array (
    'host' => 'localhost',
    'port' => 6379,
    'timeout' => 1.5,
    'dbindex' => 0,
  ),
  'default_language' => 'pl',
  'default_locale' => 'pl',
  'auth.webauthn.enabled' => false,
  'overwriteprotocol' => 'https',
  'htaccess.RewriteBase' => '/',
  'simpleSignUpLink.shown' => false,
  'maintenance' => false,
  'updater.release.channel' => 'stable',
  'music.lastfm_api_key' => '****',
  'music.cover_size' => '400px',
  'integrity.check.disabled' => true,
  'enable_previews' => true,
  'default_phone_region' => 'PL',
  'enabledPreviewProviders' => 
  array (
    0 => 'OC\\Preview\\PNG',
    1 => 'OC\\Preview\\JPEG',
    2 => 'OC\\Preview\\GIF',
    3 => 'OC\\Preview\\BMP',
    4 => 'OC\\Preview\\XBitmap',
    5 => 'OC\\Preview\\Movie',
    6 => 'OC\\Preview\\MP3',
    7 => 'OC\\Preview\\TXT',
    8 => 'OC\\Preview\\MarkDown',
  ),
  'theme' => '',
  'loglevel' => 2,
  'logtimezone' => 'Europe/Warsaw',
  'twofactor_enforced' => 'false',
  'twofactor_enforced_groups' => 
  array (
  ),
  'twofactor_enforced_excluded_groups' => 
  array (
    0 => 'Użytkownicy',
    1 => 'admin',
  ),
  'app_install_overwrite' => 
  array (
    0 => 'audioplayer',
    1 => 'music',
    2 => 'metadata',
    3 => 'groupfolders',
    4 => 'bruteforcesettings',
    5 => 'apporder',
  ),
  'updater.secret' => '****',
);

The output of your Apache/nginx/system log in /var/log/____:

[Sun Aug 15 00:00:02.584819 2021] [mpm_prefork:notice] [pid 1083] AH00163: Apache/2.4.48 (Ubuntu) mod_fcgid/2.3.9 OpenSSL/1.1.1f configured -- resuming normal operations
[Sun Aug 15 00:00:02.584955 2021] [core:notice] [pid 1083] AH00094: Command line: '/usr/sbin/apache2'
[Sun Aug 15 02:26:34.719787 2021] [mpm_prefork:notice] [pid 1083] AH00170: caught SIGWINCH, shutting down gracefully
[Sun Aug 15 02:26:46.798368 2021] [mpm_prefork:notice] [pid 1082] AH00163: Apache/2.4.48 (Ubuntu) mod_fcgid/2.3.9 OpenSSL/1.1.1f configured -- resuming normal operations
[Sun Aug 15 02:26:46.800830 2021] [core:notice] [pid 1082] AH00094: Command line: '/usr/sbin/apache2'
[Sun Aug 15 02:26:58.514415 2021] [authz_core:error] [pid 1266] [client 127.0.0.1:54178] AH01630: client denied by server configuration: /media/pawel/Seagate