1) Press both Button 1 & Button 2 and see if 'Go to OLED test' is showing.
If it doesn't, a comprehensive test of the device is necessary. Please contact the seller for returns or refund.
2) If the 'Go to OLED test' normally shows, press the button for the 'v' on the top of the screen and keep continuing to next step.
At the final stage, press both Button 1 and Button 2 at the same time and see if it ended normally.
If it does, re-plug the cable once, and the device should start normally.
* For any further question, please turn to the Q&A page or contact the seller.