After the error message the Encryption Unsuccessful appear, choose ‘Reset Phone’ at the bottom of the message, and your phone will reboot automatically and booting to recovery mode, and wipe the data cache. Just wait the process until complete.
After done with wiping data and cache, the phone will reboot automatically. For the first booting, it take time for two to three minute. So, you must to wait quite longer.
If the issues are still persist, remove the SD card out, and then format the SD card with FAT 32. After it, back the SD card in to phone and then repeat the process like mentioned above.
Doing the factory reset in recovery mode by tap and hold the power and volume up button, choose Wipe the data or factory reset’ option.
If this method still fail to fix it, and then boot in to factory mode by tap and hold the power and volume down button. It will display in China language. Choose the option which has “eMMC” in its name, and wait the process to complete. And then reboot your phone again.
If all the method mentioned above still fail to fix the problems, the final method is to flash back with upgrade firmware method. So, make sure the firmware stock that you used for flash included usrdata.img and cache.img files.