It's almost guaranteed that the solder joint is bad, as this is a known problem with the A3000D led panel. Every time you close and open the case, the leds are a little pushed, and after doing this for 10 or 20 times, the solder joint finally gives away. You can either fix the joint and support the leds from now on by reinforcing them with some rubber glue, so that they can't move or be pushed easily, or solder wires going directly to the led pins to the motherboard connector(s), and not have to worry about movement of the leds ever again when opening and closing the case.
