Dear @rgangara
Apologies for the delayed response. From your request we can see that you have entered 2 in the quantity field, which is not allowed. Only Multiples of the Lot size are allowed in it. If you want to buy 2 lots of BANKNIFTY, please enter 2*15, ie. 30 in the request. If you are still facing this issue, please share request and response on smartapi@angelbroking.com.
Regards
SmartAPI Team