For anyone experiencing issues on older versions of SE (v0.990.46.1955 or older), there's an easy fix to this, described by DeMooniC (Thank you!):

DeMooniC 님이 먼저 게시:

WARNING! This addon won't work in some older versions, due to SE not being able to read the ".pst" extension of the model script, found at "C:\Program Files (x86)\Steam\steamapps\workshop\content\314650\2634871133" where you then have to open "Milky_Way_Overhaul_v602.pak", then models folder, galaxies and there you find "NMilkyWay.pst". All you gotta do is change the extension from ".pst" to ".cfg", also delete cache folder before starting SE.

Let me know here of any issues related to older versions.