BO Not accepting BANKNIFTY18NOVFUT as valid instrument trading symbol

I am trying to post BO orader for bank nifty future.

Here is the data I am posting to zerodha using API calls.

product=MIS&quantity=20&squareoff=310.0&stoploss=30.0&price=12.0&tradingsymbol=BANKNIFTY18NOVFUT&exchange=NSE&validity=DAY&trailing_stoploss=5.0&transaction_type=BUY&order_type=LIMIT


And in return I get following error.

{"status":"error","message":"Unknown instrument","data":null,"error_type":"InputException"}

I have taken the trading symbol from the CSV file which I have downloaded using API call.

Kindly help me with this as I am struggling on this since couple of days.

Thanks!!