The obvious one, did you change the IP address to be compatible with your network?
My problem was with an Olimex SAM7-EX256 board where the PHY address was not correct. You have to carefully review the PHY documentation to see what the default address is and how it is reprogrammed. The FreeRTOS example was not compatible with the Olimex design PHY (KSZ8721BL). If you are sure you received ARP packets, I doubt this is your problem.