this disk is offline because of a policy set by an administrator  

This is new : )

Plugged in an external 2TB USB drive that I have had no problem accessing before. No new updates no new programs installed since the last time I used it. Hard Disk Sentinel does show bad sectors but the app has been showing this message for over a year now and it has not changed. It still shows the exact same number of bad sectors. I thought HD Sentinel was the offending program but when I exited it no go. When I go to the taskbar I am able to easily enough eject it. My backup computer died on me a couple of weeks ago. I can not recall but the last time I think when I plugged it into a public computer it was blocked. At the moment I do not have access to another computer. When I go into disk management I can see the drive but I also see that offending message "this disk is offline..." I GOOGLED this and saw quite a bit of info but before I go scurrying around for a possible fix I thought that I would ask here first hoping that there is simple solution. I have made no changes in the GPE since the last time I plugged in the disk which showed right away in explorer and I was able to work with it. TIA.

Hello!
From the photo of Disk Management I see no drive letter is assigned. I have seen this bug before. Try right-clicking on the partition area on Disk Management and select Add drive letter. Add the next available drive letter and now you should be able to access the disk.

spapakons said:

Hello!
From the photo of Disk Management I see no drive letter is assigned. I have seen this bug before. Try right-clicking on the partition area on Disk Management and select Add drive letter. Add the next available drive letter and now you should be able to access the disk.

Thanks for responding. I have seen this as well and very recently. With my 8yr old backup computer every time I loaded up the docking station with 2 Two TB storage drives nothing would come up. Frankly it took me forever to find the solution which is as you point out just run disk management and create and format pops up and then right click and add a drive letter and it pops back up in explorer. This was the first time however I saw it with my new computer (12/2017 Thinkpad p51) and I had just successfully mounted the external 2 TB USB drive just a week or so ago. Sadly when I right clicked that was when I got the message "this disk is offline because of a policy set by an administrator" and I was unable to add a drive letter to make it come back up in explorer.
Yesterday I took the drive to a public computer and it did in fact pop up in explorer so that was good news. This morning I was just about to go all Internet crazy on this b*tch when I tried plugging it in again and again I got that error message. However if you click on the first pic I uploaded it will enlarge and you see right next to "Disk 2" that error message well for whatever reason I right clicked on that red error "icon" and it asked me if I wanted to put the disk back online and I clicked you betcha and it "magically" appeared in explorer!

Good news. However its health is very low and you risk losing everything at any moment. I recommend buying a new 2TB or greater disk, copy all contents as long as you still can and then send it back to store for replacement under Warranty. Make sure you backup everything first, they will just replace the disk and won't mind your data!

spapakons said:

Good news. However its health is very low and you risk losing everything at any moment. I recommend buying a new 2TB or greater disk, copy all contents as long as you still can and then send it back to store for replacement under Warranty. Make sure you backup everything first, they will just replace the disk and won't mind your data!

>However its health is very low

Great minds think alike. According to Hard Disk Sentinel the health of the drive has remained the same (no additional loss of bad sectors) ever since I first noticed the health of the SIX YEAR OLD inexpensive 2TB external drive about 7 months ago and coincidentally a Western Digital 4TB bare bones drive happened to be on sale which I purchased and backed up the contents to the that. Over this past summer there were a few times when I did not feel like dragging out the docking station so I just used the "iffy" drive to store some stuff and I had only gotten around to transferring that over to the 4TB drive the other day when I ran into the problem of it being unable to mount in explorer.