Some heavy-duty removable hard drives may even have to be plugged in with a separate power cable before they'll work. Next, open the Disk Management tool. To do so, press Windows Key + R, type diskmgmt.msc into the Run dialog, and press Enter. You should see your external drive listed in the Disk Management window.
1. Rule out hardware damage: Can other pc detect or hard drive?
A. If yes=your pc is the problem
a1. Check ports, or you might assign a drive letter to your device, a program might preventing it from opening (e.g. anti virus or anti malware software)
B.If no=your external hdd is the problem
b1. Check cord/use another, determine if it is still spinning. There are tutorials in YøùTùbé on how to salvage it but only at a very low chance.