Weird! Maybe it's permissions somehow afterall. Glad you figured out a workaround in any case. If you're playing on a pc, I wonder if you'd have the same issue working off a 2nd HDD.
I'm not exactly sure it has something to do with permissions as I even tried changing the folder permissions to allow full access to all users, but then again, I just remember my flash drive is formatted in FAT32 for some reason, so NTFS folder permissions are removed when a folder is transferred to a FAT32 drive, allowing anyone or any thing that interacts with the folder full access 100% of the time. If I get around to getting an external hard drive or at least an adapter, I'd try it out on a second HDD, but for now this is what I've got to work with.
I've had trouble with file sharing permissions settings before that felt like black magic to me (I never could figure out the inconsistencies after looking it up and trying over and over again). That was after wiping my HDD and reinstalling Windows as well - so same premise as you have. Thankfully my issue wasn't with Strive at least and I did get a workaround that's still "working" for me. Anyhow, I'm glad you got it working.