Two thoughts come to mind. Firstly you need to make sure the web server has the appropriate print drivers installed. They are usually different versions to your client machines (e.g. your dev machine) If you log onto the server and try printing e.g. a text file manually it will confirm to you whether printers are installed on there.

Is the web server in a DMZ by any chance? If it is sitting on the other side of a firewall to your internal network where your printers reside you might need to allow it through the firewall.