Re-join the network after the coordinator sudden power down. Xbee 802.15.4

Hi there,

When I set up the network, I have one coordinator and a few end points.
I use Xbee S2C 802.15.4 to set up this network.
When there is power down on the coordinator only and power recover after one or two minutes.
I set up the network allowing the network to change the channel.

When the power is back up and running. The coordinator is no longer in the network and receiving any message from the end points.
I guess the coordinator is back to the original channel. And the end points those didn’t have the power cut problems are in different channel.

In this case, please advise me how do I recover the network and allowing the coordinator to find the original end points after power cut.

Thank you.