M8024K not responding serial port

I have two switches 8024kinstalled on a Dell Chassis  and I need to change the out-of-band IP.

1.-  Via Chassis CMC GUI I can see t the IPs of the switches but they are grey out.

2.-  when I tray to access them via serial port, they are not responding. At the putty prompt  I cannot type anything.

Is there any other way I can access the switches? What could be the reason a serial port t is not responding? 

I can access other switches via serial port but not this ones.

Any Ideas will be appreciated. Thanks