Connect a PC to it with a crossover cable and change the PC's address to the old range, then scan the subnet. Alternatively reset it to defaults - default IP address 192.168.254.254 or 198.102.102.254 according to
http://www.zebra.com/id/zebra/na/en/documentlibrary/manuals/en/ZebraNet_PrintServer_II_Users_Guide.File.tmp/45537L-004rA_Final.pdf