[Q] SuperSU launch error

Hi All....Please help me with a error that I have in launching SUPERSu.

A few months back I networked unlocked my phone and it was working fine. I returned to India today and my SIM Card is asking for network unlock key again. Why did this happen? Is there not a way to network unlock the phone for ever? Where is the home network configuration stored in the phone?

I tried using SuperSU but it does not launch. I get an error "There is no SU Binary installled and SuperSU cannot install it. This is a problem". How do i get over this? I tried uninstalling and re-installing from Play Store but that does not help.

Thanks in advance for your help.

Regards,
Guddu