Looking at the information page it says the network card is disconnected. Is there a way to reset the network card? This printer has worked fine for many years, suddenly it is off-line and cannot get it back on the network by either DHCP or manual TCP/IP connections.
Assuming you have checked the cable and the port, go to
Printer Setup > OK > Connection Setup > OK > Reset Connection Setup > OK > Reset Connection Setup Now > OK
Next step is the nuclear option, reset it back to factory defaults via:
Troubleshooting > OK > Service Tools > OK > Reset NVRAM > OK > NVRAM > Reset Printer NOW > OK
If it won't work at that point the hardware has failed.