RCM5600W debugging serial port problem

Dear visitor

I have two RCM5600W boards.
One of the board when I plugged into a computer, it detected serial port as port 3(USB) and it can communicate with computer very well.

Meanwhile the another board when plugged into computer, it detected as port 5(USB) and it cannot communicate with the computer. It give error like

“While Sending Bios:
Timeout while waiting for response from the target”

i try to choose a slower baud rate and it just stopped when compiling to the board.

Anyone have the same problem? can help me to solve the problem?