When you self test the printer, does it say “Parallel Interface or other”? Awhile back I had a couple Epson TM-U220 Micros printers that wouldn’t change from Serial no matter the dipswitch setting. It had to do with the specific model of TM-U220.

Here is a link to tell you all the dip switch settings. The card with 4 dip switches on it is the Type 3.
https://www.beaglehardware.com/howtoethernet.html