Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
First, you may not have installed the drivers for your Roland DGA printer. Go to this site:http://www.rolanddga.com/owners/support/
enter your printer's serial number, and search for appropriate driver(s) or updates.
But - if your computer is one that was already working, printing, to the SC-540 printer - then it presumably has the right drivers. In which case, the network setup you have, is likely not what that computer and that printer worked through.
In fact, your computer probably has, in its printer driver, a wrong IP address
for the printer. That could make it quite incapable of printing.
Also, your switch may not be allowing communication to the printer from the computer. You should go into the switch's setup, and open communication to the printer's current IP address (whatever it is) from the computer's current IP address (whatever it is).
(And to make that work "permanently", you need to have both the computer's IP and the printer's IP, fixed or non-DHCP