RCST's not taking new IP address.

Hello Dear Experts ,

Need your help urgently .New RCST's on the Linkstar network comes up but do not take new IP address.Old RCST's on the newtork if assigned with a new IP address not responding .Only existing RCST's with its corresponding IP is working .

Please advice what can be done to allow addition of new RCSTs into the network.

Thanks in advance to all experts.