It can be extremely frustating when you know your external hard drive is working but it will not show up in Windows. It just happened to me not long ago, I tried everything under the Sun, driver update, properties, etc.
My device, a USB 3.0 2TB Western Digital HDD had been plugged in multiple times in the past without any problems, suddenly it was not being recognised by Windows 7. I have it fully encrypted with Truecrypt but the same problem might happen if you use Veracrypt or any similar software, this is a Windows problem.
The first thing to do is to make sure that Windows has acknowledged your device, it can be done three ways:
Launch command prompt entering cmd.exe in the search box. Now type: diskpart a new window will be launched, now type: list disk you should see your deviced listed.
Open Windows Device Manager typing Device Manager in the search box, click on it check the arrow that says “Disk Drives”, your external hard drive should be listed there.
Go to the “Safely Remove Hardware and Eject Media” icon in the Windows taskbar, click once on it, your USB device will be listed there if it has been recognised.
Whichever way you use, now you know for sure the device is recognised.If it does now show up the problem will be hardware related, cable, USB port, fried device, etc.
Now you launch your encryption sofware, in my case Truecrypt, I clicked on “Select Device“, it lists the external device listed as Hardisk 1 (screenshot below).
Windows will still not show up the drive letter but since it is listed with your encryption software, selecting it and mounting as normal entering the password your encrypted drive will be displayed as it always has, it will work.
The problem appears to be that with the time your operating system becomes more unstable due to junk left behind and Windows has problems with drivers and what not. The only solution to have again an operating system that boots fast and recognises all external devices at once is reinstalling Windows.
Cleaning junk will help speed up Windows, I use WiseCare365 for this (freeware version), but nothing will never be as good as a clean reinstall.