Cant upload Bluno Firmware

I am following the method to upload the Bluno firmware to a blank CC2540 chip as mentioned procedure here -

https://wiki.dfrobot.com/How_to_flash_a_new_CC2540_chip_with_DFRobot_BLE_service?

I have designed the circuit using the reference schematic - 
http://www.dfrobot.com/image/data/DFR02 ... %20Sch.pdf

I can flash the bootloader 2.0 successfully with CC Debugger and can see two LEDs flashing alternately.

But when I tried to upload the firmware "SBL_Bluno_V1.96" using Bluno firmware downloader 1.0, it started and run smoothly and after a while, in the middle of the firmware upload process, it stopped and showing msg "Download Stop". Consequently, the bootloader is getting corrupted.

Can somebody tell me why I am getting this error ?? I tried several times but same things happened.

I am using Windows 10 Home Edition 64 bit.