External hard drives are very susceptible to be damaged from being dropped simply because they sit in high traffic areas and they get knocked over or moved around often.

Hard drives that have suffered a power surge will normally affect the printed circuit board (PCB) and stop the hard drive from spinning up.

There are endless possibilities why your hard drive is not booting up. But for the purpose of educating you here we can assume that the problem is one of the most common problems we see and that would be bad sectors.

There are 3 main reasons a hard drive will not spin up. Bad fluid bearing, bad motor, but the most common problem is the printed circuit board (PCB) may become damaged.