What type of firmware did you try to flash? A or G?
Check in your settings what type of firmware you allready have and flash the same type of firmware (don’t forget to “Clean data” - it will delete all the data on the phone, so save all your important data on your PC).
After you update to the latest firmware you can switch types: A - being for Chinese Firmware and G - for Global firmware.
Check the guides on General Chat to see how to switch firmware versions - but only after you have upgraded to the latest firmware that you allready have!!!
Hope it helped you.