Idea Cellular — sim card not getting recognised

Address:

Mumbai City, Maharashtra, 400008

I have been using my idea prepaid number for 2 years now as my second sim.
I had shut off my sim 2 slot for 1 month as i was travelling internationally, and upon putting it back now it is not getting recognised at all.
It is very important that this is activated at the nearest possible date, as i use this as my office sim and people are trying to reach me urgently on this number. Please suggest what is to be done