For the HelioPanel File Manager, file permissions are very important. The HelioPanel File Manager acts like one of your own PHP scripts; it requires the appropiate permissions in order to read/write/execute on files. If the file permissions on the file you wish to view or edit are not correct, HelioPanel will be unable to perform the action you request. File permissions cannot be changed within HelioPanel, so you must do it using FTP or cPanel.
File Permissions are the permissions set on each individual file or folder. For example, a folder is usually 755, while a file is usually 644. When a file is inside the cgi-bin, the permissions of the file should be 755 in most cases. The first digit stands for Read, the second for Write, and the third for Execute. You can research more about file permissions online.