ESP32-POE-ISO-IND fails Ethernet.begin()

I've just got ESP32-POE-ISO-IND and trying to get ip address through DHCP. I'm using Arduino framework with arduino-libraries/Ethernet@^2.0.1 My code would be like:

#include <Ethernet.h>
  byte mac[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED};
  int result = Ethernet.begin(mac);
  Serial.print("Ethernet.begin ");
  Serial.println(result);

The problem is that begin method always returns 0 (AFAIK it should return 1 when successful https://www.arduino.cc/reference/en/libraries/ethernet/ethernet.begin/).

The question is why it doesn't work. Is it MAC the problem as I just copied the one from sample code?

OLIMEX / ESP32-POE

ESP32-POE-ISO-IND fails Ethernet.begin() #34