Yeah, mine did that after being unpowered for just a few days.
A general tip is to take it apart and unplug the cable for the display. Then turn it on and if it boots, replug the cable.
That worked for me 1 time.
Next time i unpowered it, i got the flash/ click again and none of the tricks you can google has worked since.
So if you ever get it working again... Never unpower.
Will post again, if i find the cause.