Maybe folder / total path names are too long? Once you get to your region containers that’s a pretty long path in all! Add on the actual addon folder names which some can be quite long. Maybe just one or a few are too long and the whole system fails.
I’d try renaming the MSFS Addons folder to just Addons or “Mods” and put it in the root of D Drive. As that seems like a dedicated drive for MSFS (judging by its name) there is no point in burying it 3 layers down?