Hello
I checked with IRCTC and here is the I got from them.
Dear Customer,
With reference to the approval from Competent Authority, iOS App is closed w.e.f. 12th April'17.
As such booking will not be allowed but cancellation should be continued through App. Customer can also visit IRCTC website for ticket history ( Old Ticket booked history mobile app) & Cancellation.
We need to find contact details of Competent Authority or should inform Railway Minster directly to resolve this.