Looks like you are running into the same issue a lot of folks have with using 3rd party board.
Per page 20 of the manual, "The only required pin connections are VCC, GND, DO
UT and DIN. support serial firmware updates,
VCC, GND, DOUT, DIN, RTS, and DTR should be connected."
The vast majority of the 3rd party board such as the one you are using is they are designed for two way communications. They are not designed for updating the radios firmware. That is to say, they do not add the additional lines that are required to upload firmware. You need to use a board such as the XBIB-U-DEV board for that.