My daughters Macbook Pro always had problems finding the hard-drive. Went through four hard drives would work for a little while, then same problem. finally would only start half the time to not at all. Tried everything I could find then GAVE UP! Fast foward about four months - she got a new one for college and let me have her old one ( I like to take things apart 
). Plugged it in, started right up, working great, updated to Sierra (while it was resting? ) she got some of her files, next morning it was back to not working. Any ideas? A connection somewhere? She had it plugged in the whole time
). Plugged it in, started right up, working great, updated to Sierra (while it was resting? ) she got some of her files, next morning it was back to not working. Any ideas? A connection somewhere? She had it plugged in the whole time