W5500 must obtain IP address using DHCP first, or you should hardcode/somehow configure valid IP address into the chip (each chip on the network should have unique IP address, as well as MAC address).
Ok, this is different story. In this situation, even if router does not display the device host name (provided through option 12) it must show the IP address assigned to the device. If it does not, then something is misconfigured, and router blocks the messaging. First of all, check MAC address you have chosen for the W5500 to be valid.