The EAP600 and ECB600 wireless access points do not have built in Guest
Network Feature. Setting up multiple SSID’s on the EAP600/ECB600
does not create a separate guest network, even when enabling station

To create a Guest Network, you would have to integrate the aforementioned
model access points with VLAN capable router. 

See article:

Using VLANs with EnGenius APs and Switches