I got the same issue and reselecting the folder didnt work
Can't find a newer thread so replying to this one.
I'm having the same problem so I went to look for the file to see what the version was, there was nothing in the plugins folder named spt to begin with, so I went the reinstall route, when I tried to reinstall it told me I needed to update the live version.
Since this is something that's happened to me before and doing this fixed it, I suggest at least checking for an update.
Although, I'm not exactly sure why the plugins/spt/spt-core.dll went missing in the first place. Currently going through the tedious task of figuring what mod may have done it.
