: While SOS can work on version 1.6.640, it is no longer "plug-and-play." It requires hunting for specific DLL patches and careful installation. For a smoother experience, The New Gentleman or a full game downgrade is generally preferred.
When Bethesda released the 1.6.640 update, it broke compatibility with the Skyrim Script Extender (SKSE64) and almost every mod that relied on a custom sos 1.6.640