Have you checked apache (assuming you are running apache) error logs?
In looking at the mdeploy.php file found at moodle code directory root, it shows that it can be executed via command line.
Here's the help on it:
php mdeploy.php --help
mdeploy.php - Moodle (http://moodle.org) deployment utility
Usage: $ sudo -u apache php mdeploy.php [options]
--passfile File name of the passphrase file (HTTP access only)
--password Session passphrase (HTTP access only)
--proxy HTTP proxy host and port (e.g. 'our.proxy.edu:8888')
--proxytype Proxy type (HTTP or SOCKS5)
--proxyuserpwd Proxy username and password (e.g. 'username:password')
--returnurl Return URL (HTTP access only)
-d, --dataroot Full path to the dataroot (moodledata) directory
-h, --help Prints usage information
-i, --install Installation mode
-m, --md5 Expected MD5 hash of the ZIP package to deploy
-n, --name Plugin name (the name of its folder)
-p, --package URL to the ZIP package to deploy
-r, --typeroot Full path of the container for this plugin type
-u, --upgrade Upgrade mode
And appears to use curl (from looking at the code). Is curl installed on system and have you tested via command line?
curl -I http://yourownmoodleserver/
'spirit of sharing', Ken