Hi @mamo,
Have you checked the file permissions on the directory specified in the files_dir directive in your config.inc.php configuration file? There’s information in the README file on what file permissions should be. If that’s not the issue, then try uploading a small file. If you can get small files to upload but not large ones, then the most likely cause is file size limits in your PHP configuration (see php.ini).
Regards,
Alec Smecher
Public Knowledge Project Team