To prevent the printer firmware from freezing when you connect the Ethernet cable, you must adjust some settings in the BIOS. Specifically, you need to disable certain onboard devices to avoid IRQ conflicts. Since the firmware runs on FreeDOS, which is not a Plug and Play OS, these adjustments are necessary.

While I do not recall the exact settings that need to be changed, I have taken photos of a working printer that can serve as a template.

Update as of 2022: I have set up a printer with a dead CMOS battery and found that you must set "Floppy Drive A" to "Not Installed".