Xbee on 802.15.04, recovery of network after power disconnection.

Hi there,
I currently use the Xbee S2C to set up 802.15.04 network.
There are a few networks in the field. Around 5 coordinators to set up 5 networks. Each network has 4 end points.
Coordinator A1=7
End point A2=7 in the setup.

I found that if one single coordinator is disconnected from power for one or two minutes. When power resumes, the coordinator can no long receiving data from end points.

I guess the end points are all still remain in the channel when the network was created. The coordinator is now in the starting channel.

Please advise how can I get the coordinator to receive the data from end points again.

We have 5 networks in the field. Therefore we prefer the network can adjust the channel and PAN ID to avoid interference.

Best regards