Error 401 when trying to share via Link (External API -- kopanofiles)

Nextcloud version : 13.02
Operating system and version : Debian Stretch
Apache or nginx version: Apache 2.4.25-3+deb9u4
PHP version: 7.0.27-0+deb9u1

Unsure if it is a Nextcloud or kopanoissue, but if I try to share a file via Link Nextcloud reports an Error 401.

Perhaps you can tell me what can trigger a 401 (unauthorized) in this situation?

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

Steps to replicate it:

  1. Connect Kopanofiles tho Nextcloud via Owncloudplugin
  2. Upload a file
  3. Choose the file
  4. Click on share
  5. Tick the option “share via link”

The output of your Nextcloud log in Admin > Logging:

nothing logged in this case

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

<?php
$CONFIG = array (
  'instanceid' => 'xxxxx2kboo',
  'passwordsalt' => 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
  'secret' => 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
  'trusted_domains' =>
  array (
    0 => '10.0.0.5',
    1 => 'cloud.at',
  ),
  'datadirectory' => '/data',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'overwrite.cli.url' => 'http://10.0.0.5/nextcloud',
  'dbtype' => 'mysql',
  'version' => '13.0.2.1',
  'dbname' => 'cloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'cloud',
  'dbpassword' => 'xxxxxxxxxxxxxxxxxx',
  'installed' => true,
  'mail_from_address' => 'edv',
  'mail_smtpmode' => 'php',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_domain' => 'mydomain.at',
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 2,
  'auth.bruteforce.protection.enabled' => false,
);

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

"POST /ocs/v1.php/apps/files_sharing/api/v1/shares HTTP/1.1" 401 4948