First test your EHDD to another PC or Laptop, if its not detected or open, then just adjust the data cable and try again, if it din work it may have corrupted for following reasons;
1. Virus Attack (Logical Crash)
2. Damaged by a Shock (Physical Crash)
both ways you can recover your data's, but its not 100% sure than you can recover it, you can use some data recovery software's to recover your files.
a piece of advise,
"External Hard Drives are Not the Best way to Backup your Data's"
Good luck !
try to connect it to another computer if it shows same result then your external drive is damaged. you can open the external drive and remove the harddisk and connect to a desktop pc to recover your data. goodluck
Sit over it or put pressure on u it by ur hand.
Try these easy steps:
1. Try to open it in different PC or Laptop
2. Try to use / change USB Cable