I'd start with Recuva (free download) to see if it can recover anything. That means: copy what it finds to another hard disk (either internal or external).
If such recovery programs (there are more, but be sure you never write anything to the disk or work on a 2 TB clone) fail, all you can do is pay a data recovery company to see if they have better tools. See the top 2 posts in https://www.cnet.com/forums/storage/ for tips.
Since it's well known that, as we say here, "you only lose what you don't backup", I assume you have a backup of the data on that disk. Then all you lose is money.
My 2T Seagate backup/Expansion drive has somehow erased since yesterday. It's passed the tests I've run on it from SeaTools .
The only thing I can think of is that earlier tonight I had trouble with a 128GB TEAM flash drive. It has Windows 10 on it for emergency reinstall. It's been used successfully to reinstall Windows 10 on my computer. But whenever I plug it into the computer, the cursor starts to jerk around and becomes very hard to use. I was trying to transfer TV episodes to it to transfer to my tablet. If I moved more than one TV episode at a time, the flash drive would become unrecognizable. I've never had Windows on a flash drive before, so I don't know if the problem is what I have on the flash drive, or the flash drive itself. It was because of the trouble with the TEAM flashdrive that I wanted to backup a movie onto the 2T Seagate drive after having to restart (because of the troubles caused by the TEAM flashdrive), and found that my 2T Seagate drive is blank!
I know there are folks out there who are not fans of Seagate. This is the first time I've experienced anything like this. When problems arise with an expansion drive, is it usually like this? The only problem I've ever had with a Seagate backup drive is when it started whining; I copied everything on it just in time as it quickly became unreadable. This, though, I didn't expect this with my new (2 year old) 2T Seagate Expansion.
Is there any way to find out what happened? There's no "Previous Versions" to look at.
How do I stop this from happening again?
Can I retrieve the data?