Please follow the steps below.
1. Turn off the power of the DDJ-SX.
2. Disconnect the DDJ-SX USB from your computer.
3. Turn on the power of DDJ-SX.
4. See if the LEDs of the Master level meter still blink or not.
If you do not see any LEDs blinking, you successfully updated the firmware.
If they still blink, you may have failed updating the firmware. Please follow the Download the update instructions to update the firmware again.
If you still see the LEDs blinking, please let us know as it may be a power issue.