If you have totally forgotten the IP address of your CG-ONE and hence can't even access the login page, follow the following steps to re-gain access.
1) Unplug the LAN cable connected to the CG-ONE to turn-on the hotspot mode of the CG-ONE.
2) Thereafter join the CG-ONE Wifi hotspot.
3) Follow the instructions in our CG-ONE QuickStart guide to access the CG-ONE and thereafter re-configure the LAN IP. See https://support.commzgate.com/hc/en-us/articles/115000085701-CommzGate-ONE-appliance-QuickStart-Guide