Regarding refund from irctc

We booked a ticket in online, the train got cancelled itself for the booked stations due to floods in kerala on 17th August, 2018.after that we tried to cancel or to file tdr, but the we didn't get the option in the web to cancel the tickets. Regarding this we sent a request mail to irctc,they replied like train was not cancelled for the given PNR. Please guide us to take the further steps to get our refund amount.