Hello Horst,

I have checked your site and it looks like the open_basedir in php is causing issues here,

Warning: is_dir(): open_basedir restriction in effect. File(/media/com_easysocial/files/groups) is not within the allowed path(s): (/var/customers/webs/silberfuchs/:/var/customers/tmp/silberfuchs/:/usr/share/php/:/usr/share/php5/:/tmp/) in /var/customers/webs/silberfuchs/RNA/libraries/joomla/filesystem/folder.php on line 481

Warning: is_dir(): open_basedir restriction in effect. File(/media/com_easysocial/files) is not within the allowed path(s): (/var/customers/webs/silberfuchs/:/var/customers/tmp/silberfuchs/:/usr/share/php/:/usr/share/php5/:/tmp/) in /var/customers/webs/silberfuchs/RNA/libraries/joomla/filesystem/folder.php on line 481

Warning: is_dir(): open_basedir restriction in effect. File(/media/com_easysocial) is not within the allowed path(s): (/var/customers/webs/silberfuchs/:/var/customers/tmp/silberfuchs/:/usr/share/php/:/usr/share/php5/:/tmp/) in /var/customers/webs/silberfuchs/RNA/libraries/joomla/filesystem/folder.php on line 481

Warning: is_dir(): open_basedir restriction in effect. File(/media) is not within the allowed path(s): (/var/customers/webs/silberfuchs/:/var/customers/tmp/silberfuchs/:/usr/share/php/:/usr/share/php5/:/tmp/) in /var/customers/webs/silberfuchs/RNA/libraries/joomla/filesystem/folder.php on line 481

Warning: is_dir(): open_basedir restriction in effect. File(/) is not within the allowed path(s): (/var/customers/webs/silberfuchs/:/var/customers/tmp/silberfuchs/:/usr/share/php/:/usr/share/php5/:/tmp/) in /var/customers/webs/silberfuchs/RNA/libraries/joomla/filesystem/folder.php on line 481

Warning: is_dir(): open_basedir restriction in effect. File(/) is not within the allowed path(s): (/var/customers/webs/silberfuchs/:/var/customers/tmp/silberfuchs/:/usr/share/php/:/usr/share/php5/:/tmp/) in /var/customers/webs/silberfuchs/RNA/libraries/joomla/filesystem/folder.php on line 481
{"message":"Objekt-Datei konnte nicht abgerufen werden","type":"error"}

You will need to actually check this with your hosting provider. If it's possible, turn open_basedir off . If it's not possible, you should request your hosting provider to add the /media/ path to the open_basedir settings.