Seems like a hardware problem. You may want to contact Onyx Boox customer support: sales(at)onyx-international.com. From my own experience with devices from the C67ML series, general troubleshooting hints may include the following steps.
1. Try resetting the device. Reset hole is just to the left from the power button. The blue led should blink once. If you hold the reset button for 2-3 seconds, the blue led will blink both when you press the reset button and when you release it.
2. Try connecting the usb power cable and charge the device from a wall socket for 20 minutes +. Try replacing the cable and the charging unit
3. Try charging the device from a wall socket with the reset button pressed
4. Try connecting the device to PC: install the drivers, start factory tool (you may need to delete the Chinese characters from the folder name), connect the device with usb2 cable and check if it is recognized by the Factory Tool
5. (warning: disassembly of the device most often will void the warranty if you accidentally leave scratches or other signs of disassembly) Try hard-resetting the device: disassemble it by taking the back cover away and detach the battery cord. Disassembly video -
https://www.youtube.com/watch?v=poJLzhlVxVI (the first two minutes)
I hope you'll find a solution. Please don't hesitate to ask here if you need additional information.