Factory reset in Recovery Mode.
If the phone fails to boot-up or hangs during power up, the factory reset in recovery mode is one of the method could be tried to fix the issue.
1st: Press the volume up key and then insert the USB cable with power. Then press the power key.
2nd: Release power key after device vibrated. The display will start as the picture below.
3rd: Then go to this screen and release volume up key. Press volume down key to select “wipe data/factory reset”. And then press power key to execute it. The phone will proceed the factory reset process and restart.
4th: Then selected yes.
5th: After reset, its show reboot now, you do reboot.
Now wait some time for boot full devices.