When uploading from a local testing server to a web server the absolute path also needs to be updated.
The absolute path is the directory where Mambo is located on the server hard drive.

This small PHP script will report the actual absolute path.
Make a new PHP file and call it something like serverpath.php
Right at the top, with no spaces before it, add this PHP Code:

<?php echo $_SERVER['DOCUMENT_ROOT']; ?>

Place (upload) this script in the directory where you want to find the absolute path.
Point a browser to this script and the path will appear in the browser.

On a Linux server, that will give you something like this example:
/var/www/example.com/httpdocs

In the Mambo configuration.php file, the above example would look like this:
$mosConfig_absolute_path = '/var/www/example.com/httpdocs';