Well, if it does not work from a pen drive either it should not work from a PC, then pen drive is inserted in the copier USB right? Not the Mac?
First off, do a Software/Network reset, this is done at the copier by logging on as the admin, select Machine Status/Tools/Troubleshooting/Resets and choose the option that resets both (No settings will be lost) then try a print, should that fail.
I suppose it is possible that the PC is using a PCL driver, and the Mac would certainly be a PS driver, so it could mean that the copier has a faulted/corrupt PS Engine. Check the webpage (Centerware Internet Services) and select Properties>General Setup>Configuration Report>Postscript and verify it is there. Should look like this:
The latest firmware for the device is 061.121.224.11800 and that can be obtained here if you do not have it.
https://www.xrxgsn.com/admin/user/spar_release.ihtml
The release code is WC75xxSpar
Installation would be as follows.
on the printers webpage select Properties>General Setup>Machine Software>Upgrades and set it to “enabled” if it is not and “apply”
Then select “Manual Upgrade” from the left and browse to where you extracted the download above and follow the directions. It will take about 25 minutes to complete and it will not be usable for that time.
If that all fails you would need to call for support, most likely the printer will require an ALTBOOT, so I would make sure to have a current config sheet available as the settings on the device would be lost if it needs to go down that route.