No correct response after clicking READ CONFIG in LTC6804-1 GUI

Hello? I'm trying to use LTC6804-1 GUI with DC590B and DC1894B.

I connected each board and my desktop.

After clicking READ CONFIG,

CONFIGURATION REGISTERS --> FF FF FF FF FF FF.

According to the user manual of DC1894B, the registers should be D9 00 00 00 00 00 00 after clicking READ CONFIG.

I think my connections are correct because LEDs on the DC1894B blink when I send any command to the board using GUI.  

What's wrong?