Is it possible that you don't have the parameters correct on here? There are quite a few steps to making the printstamp show up correctly. First you have to have the print stamp box checked in the print screen, then Additional options window. Then type Print Stamp in the command line, and set the parameters. If you are at all unsure of what the options are it will say in the help options.
As far as size location etc, I usually have my text size at around .125" and the offset of the text from the edge at ".2,.2". Have it set to the BL corner. Hope this helps.