If you get ERROR : S_BROM_DOWNLOAD_DA_FAIL (0x7D4) , reinstall VCOM drivers and try a different USB port (preferably USB 2.0).
: Download and extract both the Winstar W30 firmware and the SP Flash Tool to your PC. winstar w30 flash file
Now for the core process. Follow exactly to avoid soft-bricking your phone. If you get ERROR : S_BROM_DOWNLOAD_DA_FAIL (0x7D4) ,
[!CAUTION]: Flashing will wipe everything on the phone. Ensure the firmware version matches your specific model exactly to avoid "hard-bricking" the device. winstar w30 flash file