In the expansion board the green led light up but not blinking, it's a sign that there is no I2c communication. I've tried to flash the firmware with no success. I also recheck all the connection between them. Still no success. can anyone help me? Can the board be service or replace certain part?
Could be many things. My first guess would be broken I2C cable, but if you are not able to flash the firmware, so maybe broken board. Do you get any communication with the board? Are you sure you have correct COM port selected?
I have noted that different USB ports may get different COM ports. So if it previously worked, verify that you are using the same USB port to connect it.
Probably then something broken. How long I2C cable are you using between the main and 3rd axis board. maybe if it is long, something has moved and that could cause interference to I2C. Or do you have the new version of board where 3rd board is directly soldered to main board. If not, I would make shortest possible I2C cable between the bards.