If the cure Firmware flashed properly the device should go into Mass Storage Mode (Kunix is a Genius). Been There Done This Many Times.
It should not boot completely.
Maybe Region 41 is corrupt (But that's another Story Altogether)
Did you use the correct Firmware for 37xx. Try again with another older version of 37xx Firmware.
Did you buy it from e-bay or similar ?
Maybe this device is not Fixable.