I have absolutely no idea what's wrong, but KSS doesn't seem to want to work for me.
I've reverted KSP to 1.3.1 on Steam, installed Kopernicus manually and with CKAN, and that seems to work with no issues.
Every time i install the basic KSS 0.7.3 gamedata, my game will give me an error message* on the main menu and won't let me load or make a new save (black screen with infinite loading).
Is this likely a KSS or kopernicus problem?
*- "Kopernicus was not able to load the custom planetary system due to an exception in the loading process. Loading your savegame is nor recommended, because the missing planets could corrupt it and delete your progress."