Ssing,
As said before you need a "null modem" the "RS232 serial" is identical
to look at but won't work.
"download not requested" is a cable or com port issue.
First, if you need to use your USB converter lead, find a driver the "prolific" driver usually work
http://www.prolific.com.tw/eng/downloads.asp?id=31 (sorry forgot how to post a link)
Then find the com port number you are using on your computer.
Go into device manager on your computer look up properties on the com port you are using and change
the baud rate (bits per sec) to 115200
then wire up the box and computer and use loader
to load firmware.
note the USB convertor lead don't normally give a very good connection
I had to give mine a couple of wiggles where it connects to the null modem cable to get it to work. It is better if you can plug the null modem straight between box and computer but on newer computers you will need the USB convertor lead.
Let us know how you get on
👍