VWAP is not available in 15 min chart for Index including the NIFTY, MIDCAP NIFTY SENSEX. At trading view it is working smoothly but not available at @Upstox
VWAP requires Volume data to be calculated. Indices like Nifty, Sensex, etc, do not have volume of their own as they are not directly tradable.
Tradingview on the other hand has built the volumes which is synthetic. It is not real volume. Synthetic volume can be inaccurate and cause users to make wrong decisions. Hence we do not provide volume on Indices.
Other brokers are providing VWAP in index using volume data from Futures.