Unable to download hex files from ardupilot firmware site

I am flashing an OpenPilot Revolution board with arduplane firmware. Have already soldered the SBL pads, installed Zadig driver and STM 32 bootloader. Can see the board in the COM port of laptop.
But when I come to flash arduplane.apj which I downloaded from the ardupilot firmware site, there is an error messgae saying no response from the board.

Not sure if my Revo bootloader is compatible with that of ardupilot or not, I downloaded arduplane with bl.hex, but all the codes show up with no choice for opening or save. How do I download this hex file ?
When I click on arduplane.apj, I was able to download to save it on desktop, but not hex file.

Any help is appreciated.