Q: the amazing reformatting USB

All right, Batfolk, riddle me this: I'm gonna be as detailed as possible since I have no clue what info might be useful, and I hope this has a really simple obvious solution that I keep missing. If so I'm ready to cut to the chase and ask someone else to tie my shoes for me because I'm tired of the knots.

So I've got this USB flash drive. It's 3.0, HP brand, 128GB. I use it to store all my music, so I creatively titled it ITUNES when I plug it in.

I've been using this drive for months. In fact I think I might have gotten it around last Christmas. Everything has been going swimmingly, nary a problem other than some slowness which I got used to, for nearly a year of use.

Shortly after upgrading to Sierra, my very important little workhorse stopped showing up when I plugged it in. I've tried other USB flash drives in both ports, much smaller in size, and they work without a problem, same as always. But no sign of this HP stick with thousands and thousands of music files that I have been compiling for more than a decade and would be devastated to lose, not to raise the stakes or anything.

Upon opening disk utility at first, I got a screen almost identical to this:

except instead of where it says Windows_FAT_32 it said, well, ITUNES. I believe everything else was the same all though I did not make notes of the fine print. I don't think the drive was actually completely full, and certainly I never got any messages saying I was close to or at capacity. I could be mistaken on this however.

Disk utility has been the only place I can get it to appear, though it does appear there reliably. I can't do anything to it besides look at the above screen and eject the drive and definitely not throw the thing across the room in a fit of pique.

Randomly, and I had done nothing new to this flash drive as I have literally been UNABLE to do anything to it, the name switched to what you see above, Windows_FAT_32, and this message started appearing when I plugged it in:

This flash drive has never been near a Windows computer. I don't actually know where the nearest one is, probably in a neighbor's house somewhere along the street. It HAS been used on a PS3 and a PS4, but that's never caused any problems before. I tried it on the PS3 and actually got it to work perfectly, but then I tried it again just now and it's no longer showing up there either. I tried it on someone else's iMac and no dice. I also went through the whole rigmarole of trying it out in boot camp, and even boot camp doesn't want it. I cleared off as much of my hard drive as I could short of a full restore just to see if that would help, and, well, it didn't.

I also tried running first aid. It works fine on my hard drive. It did not work on the USB drive until I did the hard drive purge, and now it works fine, but as far as I can tell this has meant nothing in terms of actually solving the problem.

I'm totally baffled as to how this could have happened. There has been literally no change in how I use it, it just suddenly stopped being compatible. All that's on there is music. Well, there might also be some videos, I forget if I deleted them, but if they're there they've been there for several months and not caused problems before. Is it a Sierra thing? If so, why do my other drives still work as usual? Size? Capacity? Did this drive really not like the new Kaiser Chiefs album? I cannot overemphasize the impact on my quality of life the functionality of this flash drive has. To tug at your heart strings, I've been sick from some kind of migraine and viral infection and possibly plague combo for like a month now, so I really don't have the energy to fight with this anymore. Please let this be an easy fix and I'm just stupid or delirious and reticulating splines wrong.

MacBook Pro, 13 inch retina, early 2015, recently upgraded to 10.12. Help me strangers on the Internet, you're my only hope.