The JetDirect 175x is a network print server. It makes the connected printer available on your network be it Ethernet or Wi-Fi, so you technically should not need any cable to access the printer form the Mac, but rather a driver so it can be found on the network.
You don't connect your Mac directly the print server with a cable. You
connect the print server to your network router with the ethernet cable.
And then look for the printer on the network from your Mac.
Also, the Print Server is unnecessary, because the 1200n printer already has an ethernet port and network capability.
If you what want is to connect the Printer directly to the Mac, then disconnect the JetDirect 175x from the printer's USB port, and connect the printer directly from its USB port to the Mac's USB port using a USB-B to USB-A cable.