Thank you so much ABraun.
For my processing, this below link is working:
DEM.srtm3GeoTiffDEM_HTTP = http://skywatch-auxdata.s3-us-west-2.amazonaws.com/dem/SRTM90/tiff/
Using this link processing is not working:
DEM.srtm3GeoTiffDEM_HTTP = http://srtm.csi.cgiar.org/wp-content/uploads/files/srtm_5x5/TIFF/