When the phone screen is black, it cannot be turned on. Press the volume button +home+ on/off button to display Emergency Dload Mde(ARM9 mode), and then press the home+ on/off button.

Hello, I'm sorry for the inconvenience caused by the product.

According to your description, there may be something wrong with the machine software. It is recommended that you bring the purchase invoice, maintenance card and mobile phone to the local Samsung service center, and the engineer will test the mobile phone for you.

I hope the above reply can help you!