First ensure the SATA cable is firmly plugged in at both ends. It is also possible that the SATA port on the motherboard has become faulty so try another SATA port if you have one spare. Also feel the hard drive with a finger to see if it is running. You should feel a very slight vibration. If you cannot feel it running then it is a power problem so check the power cable connections. Of course the drive could have failed but at least you can eliminate those possible causes first.
This thread is now locked and can not be replied to.