Thanks @molnarkaroly for your reply.
I got two rephone kits. I was able to update the firmware the first one without any issue on Windows 7.
For the second one, after several tries, I was able to update successfully using the following method on windows 7
- Unplug the board from PC and disconnect the battery.
- Plug the board to PC without any modules connected to the board and without sim card.
- Open the firmwareupdater.exe
- Connect battery
- Power on the board and wait for green LED
- Switch on board and press download button on FirmwareUpdate tool.
- When FirmwareUpdate tool asks to reboot the board, Press and hold the on/off button on board to reboot while connected to PC. The bright green LED turns changes to dim red colour and you should see the download progress successfully
I hope someone will find a better way but this process is really annoying