UNIFLASH: Uniflash can not open COM port

I am trying to use 232 and Uniflash to load image.I use usb to ttl to connect with PC.

but the board can not load image.Uniflash can not open the COM port.

I see the PC always sent 00 to 232 and there is not feedback.

I use 5V3A power.

I want to solve this problem and load image.

Can someone help me?

thank you so much