Windows 10: Laptop has recognized my Seagate External drive for 3 days - Not now

The Seagate Backup Plus 4TB has all the files I recovered after I got hacked in July. I had made a backup of my primary SATA drive onto a WD Passport Ultra before doing a format of the hacked/infected drive. That WD Passport failed so I had to buy a new exteral drive to recover files to.
Recovery went well, but my desktop PSU died 2 days ago, so I've been using my laptop to organize the recovered files on the Seagate. All has been going well but late yesterday evening, after a restart - Seagate was not there anymore. I tried moving the power plug to two other places, no help. The laptop has 3 USB ports, and I tried plugging into all 3 - no go. It's not seen by Windows explorer, Dir Opus, Disk Manager, nowhere.
A while back on my Desktop PC I had to go into disk Manager and assign drive letters after I partitioned the Seagate. But now it's now even showing up there.
I remember a time when there was a place where you could go and tell Windows what drive letters could be used. Well the laptop has gotten all the way up to drive I by using flash drives and two esternal drives. That's the highest the drive letters have been on the laptop, so I'm hoping Windows just needs to be told that this drive exists.
I've had some rotten luck with hard drives, motherboards, PSUs, I could go on and on. But if this Seagate (2 months old) has failed, after me getting to the point where all I had left to do is organize the data........... *Mad
I swear I won't touch another computer!! I can only hope it's a bad power cable (this one is not USB powered)
Any of you have any thoughts on the drive letters having to be assigned?
I should point out - I have a Sata USB Drive Enclosure with my Desktop 1TB drive in it. When I had both of those external drives to the laptop, Windows assigned the letters kind of weird. It gave drive F and I (2 partitions) to my Desktop internal drive in the enclosure. And it gave G and H the letters to the Seagate 2 parts.
That enclosure is working today, and still using drive letters F and I. I've not had any flash drives in the laptop since I up the Seagate.
Any ideas that will keep me from starting to throw things?? Computer related things...

Thanks folks.

:)

 

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