Go to the Exchange listing for NSE on IB¡¯s website. Select ¡®Indices¡¯ as the product type. Then you will see that there are several contracts that begin with ¡®NIFTY¡¯, but they all have some kind of suffix, such as ¡®NIFTYIT¡¯ or ¡¯NIFTYOIL¡¯. In other words, ¡®NIFTY¡¯ is not a valid symbol (which is exactly what the error message is telling you).