How do I add an XBee Gateway to an existing XBee network without resetting the network?

I’ve successfully configured an XBee network using 7x XBee S2C devices.

2x XBee S2C units are configured as End Devices, Low Power (Battery Operated) Telemetry Devices which sleep for 300 seconds then very briefly wake and transmit 1 analog value and the supply voltage then sleeps again.

4x XBee S2C units are configured as Routers, Always On (Mains Powered) Telemetry Devices which transmit 1 analog values and the supply voltage every 60 seconds.

1x XBee S2C units is configured as Coordinator running in API mode. Always On (Mains Powered) Data Receiver. This unit is receiving all analog values and supply voltages from the 2x End Devices and the 4x Routers.

For several weeks all components have been working fine and the telemetry data is being received. Great!

I’d now like to replace the XBee S2C Coordinator with the XBee Gateway (Coordinator).
I’ve connected the XBee Gateway to my LAN and configured the XBee network settings to match my current network PAN ID (ID) and Scan Channels (SC). I then turned off my current XBee Coordinator and applied the settings to the XBee Gateway. The XBee Gateway then created a new PAN Identifier (OI) and can’t detect/communicate with the existing XBee network.
Is there a way of manually setting the PAN Identifier (OI) on my XBee Gateway?
How do I add an XBee Gateway to an existing XBee network without resetting the network?

I really don’t want to reconfigure my current XBee network as some of the sleeping End Devices are hard to get at.

BTW I’m using the latest XCTU v6.3.10 application on a Windows 7 (64bit) Workstation. All XBee S2C devices are running the latest firmware (4060) and the XBee Gateway is also running the latest firmware (3.2.22.11).

Use Digi Device discovery to detect the Gateway, double click on it
then go to Red Xbee, if your network is not visible yet, click on the button that says “discover Xbee devices”, if this does not work you can change the PAN ID of the gateway in that same tab. regards