The Troubleshooting documentation page brings the following information on log files:

If all the requirements are met but you still have problems, it is recommended to check any errors present in the log files.

The default error log is <eZ_Publish_root_folder>/ezpublish_legacy/var/log/error.log in the eZ Publish installation directory.

The Apache error log (usually found at /var/log/httpd/error_log on Linux systems) is also a good source of information. It usually contains errors from both Apache and PHP, unless the php setting error_log has been set up to log php errors to a different file.

It should have also information on ezpublish/log folder.