If you get an error like this, it means that shell_exec is disabled in the php.ini file. To re-enable it, you need to do the followng
- SSH to the server
- edit the php.ini file (on cpanel it’s /usr/local/lib/php.ini)
- search for the line that says “disable_functions”
- remove shell_exec from this line
- Save the file, and restart apache.
If you do not have root access to the server, then you’ll need to ask your hosting provider to do this for you.