I am also currently having this issue on my Mod.
I realized that the steam workshop renames the file when it moves it to whatever the name of the mod is on the workshop. So I removed the "/" I had in my mods name, but that still has not fixed it yet.
My mods name is Paladin Class. Originally named Holy Hydrosophist, it works fine if you manually copy it over to the mods folder, but doesn't work if just subscribed.
Okay, I may have figured out the issue. My issue has been fixed as for I discovered that I had missing/invalidated metadata when publishing/updating my mod.
Based off of what I can tell, both the Project Name AND Project description can't have any characters that wouldn't be usable when renaming a folder on your desktop. Apostrophes thus invalidate your mod when trying to publish it.
I removed all of them from my description and fixed my issue. Perhaps the same will happen for you?