Symptom:
Not able to enable redudancy of the Controller from NCS

Conditions:
The issue that I had with HA of controller are 

1.I already had the primary controller in controller list in NCS
2.Disabled the redundancy by going to Configure-->Controller-->Redudancy
3.When disabled both the controllers got restarted and unpaired
4. I went to secondary controller and configured ip address so that It can act on its own
5.When tried to enable Redundancy through NCS on Primary controller,The primary controller is not restarting and not trying to pair(I also restarted secondary by going to the console) but when I tried to enable SSO from Controller the controller get restarted 

The second issue that I have is 
After Unpairng controllers I added secondary controller to NCS (as the secondary controller is acting as a seperate controller) 
Although It got added I am not able to see the controller in the controller list 
So I tried one more time the error message that I got "Controller is already in domain " but I am not able to see the controller