The problem has been discussed here before and was resolved by replacing the cables, fixing the orientation of the sound module, touching the screen after the phone has been turned on (with the 2s button press), but none of those measures helped my case. When plugging the USB power, the phone led displays a dim red and than switches to a bright green. Pressing the button for 2s (or longer) does nothing, the led doesn’t change, the screen doesn’t come on. I replaced all cables twice, tried without the sound module and with, double checked orientation of the sound module, tried with and without SIM, now I am quite out of ideas. Any one?
Thx
Rafael
But does it have the battery attached? 
Have you checked the vxp flies in the mass storge? Or have you tried to copy the lastest vxp to the mass storge?
github.com/WayenWeng/RePhone_Create_Kit_VXP/
Thanks jianzhang.su, updating to 6.4 (I had 6.2) made it work!