Previously functional USB3 external hard drive shows not initialized

Have a 1TB Iomega USB3 external hard drive that worked well on both a desktop and laptop Win7/64 system. Now it shows up as unidentified and not initialized using computer/manage/storage/disk management. Disk Management also gives the optiin to initialize it but I declined because I would like to recover the data. The power light comes on and it spins up with both a USB3 or USB2 connections and is identified as an Iomega eGo drive when I use the USB eject function.
Hard Drive Sentinel does not recognize it at all. Any suggestions appreciated.

1. Please post a screenshot of Disk Management with your external HDD plugged in. Disk Management - Post a Screen Capture Image

2. It would indeed be prudent to recover the data before you try anything else on the HDD.

You may try to access the hard drive booting into a live Linux CD/pendrive.

Download Lucid Puppy (Ubuntu-Compatible Build) v5.2.8 ISO from http://puppylinux.org/main/Download%20Latest%20Release.htm

It is light and only 132.6 MB.

Make a Bootable pendrive with Rufus v1.3.2 (442 KB) http://rufus.akeo.ie/

It takes less than 2 minutes to create your bootable live Linux pendrive.

For more guidance on the recovery process directly get into the heading Recovering files from the non-bootable Internal Drive - applicable to recovery from any hard drive - in Lucid Puppy way to recover files from a non-bootable computer

You may also use this tutorial by Golden https://www.sevenforums.com/tutorials/256518-peppermint3-create-live-cd-dvd-usb-use-emergency-backup.html to create your bootable pendrive with Peppermint3 Linux.

Lucid Puppy or Peppermint3, in either case you can use Rufus to create your bootable pendrive.

Attaching full screen capture from Disk Management Screen. As stated before it shows Disk1 as unrecognized and uninitialized with the option to initialize.
In the process of downloading Lucid Puppy and reading links for recovery. Have zero experience with Linux/Ubuntu so will update if issues arise. Thank you for your update and suggestions. Much appreciated.

Ok, in your case you will be mounting both the external drives, the one to be recovered and the one to which you want to backup. Identify these by their capacity.

( Before booting into Linux, plug in both your external drives.)

If you understand the principles it is so easy. You need not know anything about Linux. ( Neither did I, when I ran that trial. :) )

What if the USB enclosure is failing?
If the hard drive can be safely removed from the enclosure it would be interesting to
see what it says when connected via SATA. The data recovery can still be run.

LL:
I should of mentioned previously that I removed the drive from the enclosure and unplugged the USB interface card. I then plugged it directly into my 3GB SATA interface on my desktop with the same results. Would spin up but not recognized.

OK, it is now your second internal drive. You can still check whether Linux can see that internal drive and show the files. If it does, you can backup to another external drive or even to your other internal drive, if space is available.

OK finally got Lucid Puppy to boot. The Active ISO burner Win7 app I was using didn't work but ImgBurn did. In case someone else runs into this the most confusing part was using lupu-528.005.iso which was a zip file as input to the ISO burn. Evidently the ImgBurn app unzips it. End of good news.
Having not a .5 clue what was happening once Lucid Puppy finally booted I could see the icons showing the three partitions of my internal hard drive on the laptop and the icon showing the DVD I had just booted from. Tried Pmount with and without mut options and the externally mounted USB drive did not display. Was able to do file displays etc on my internal drive but could find no way to find anything about the external hard drive. Any suggestions on how to use Lucid Puppy to display external drive?

I did follow your instructions and made a bootable pendrive via Rufus on a 16GB Sandisk Cruzer but my laptop had no provisions in the bios to boot from a usb device hence the DVD creation.
Yes I see the advantages of using a pendrive if your bios allows you to boot from it. In my case Lucid Puppy was booted from DVD successfully with the external drive in question plugged in BEFORE boot and Lucid Puppy did not recognize it but did recognize the internal drive. Everything in your guide assumes bios supports usb boot and once booted all the copy instructions assume Lucid Puppy recognized the external drive which it did not.
I also tested another known good external USB3 drive on Lucid Puppy and it was NOT recognized on the USB3 port but did work on a USB2 Port. The failing USB3 ego drive not only failed on the USB2 port but hung the system during boot. Does Lucid Puppy support USB3 or do we need special drivers?