Cover orders are not working

Through Kite connect api , I tried placing cover orders.
The orders are not getting placed...
My syntax for cover order placement:

try:
order_B = kite.place_order(tradingsymbol=symbol,
exchange=kite.EXCHANGE_NSE,
transaction_type=kite.TRANSACTION_TYPE_BUY,
quantity=qty,
order_type=kite.ORDER_TYPE_LIMIT,
product=kite.PRODUCT_MIS, price=ltp,
trigger_price=SL_trigger,
variety=kite.VARIETY_CO, validity='DAY')

logging.info("Order placed. ID is: {}".format(order_B))

except Exception as e:
logging.info("Order placement failed: {}".format(e.message))

help me with this issue...