Not that , every downloader have this problem.
this problem is created as NSE has changed the name S&P CNX NIFTY to CNXNIFTY and this url is hardcoded in all the downloader. till the respective coder changes the url, this problem exist.
only feasible option - is to use Subha Laabh Downloader - as it downloads the actual pr.zip file from the official site and the proper naming convention is used and the data is available for NSE Nifty spot
this is for general info - to provide solution for proper data download
rgds
subroto