I hab the same problem after flashing the original Android 6 Version.
Thats the way I solved it:
1. Starting SP-Flash Tool again and use the same scatter file as before but uncheck everything.
2. Load a OTA flash file from this board and unzip it.
3. Check preloader and in the right box of it click right and select the preloader file from the OTA flash file.






4. Hold Power and Vol up button and connect cable it should now load the preloader
5. Disconnect the phone and power up.