Sorry,
with the / character only works locally (xampp) by creating the folder in the root c :/ media/k2/attchments
but online not working.

Jose

Now everything is working properly
I modified the file administrator/components/com_k2/models/item.php
to add the path to the directory

line 496
before:
$path = $params->get('attachmentsFolder', NULL);

after:
$path = JPATH_ROOT.DS . $params->get('attachmentsFolder', NULL);

line 1021 :
before:
$path = $params->get('attachmentsFolder', NULL);

after:
$path = JPATH_ROOT.DS . $params->get('attachmentsFolder', NULL);


Jose

Great, thank you, works!