Hi guys. I had a huge issues understanding what's going on with this mod and since I remember using it before, I just had to install it again when I came back to KSP1.
Now, zer0Kerbal, I want to thank you for all the hard work you're doing managing the new version of SpaceY and for all people who have trouble getting it work, I have a solution.
1. Parts are missing. This one got to me but after reading all the comments I came to a conlcusion that parts are missing and this is not a bug. These are not ready yet, Am I right zer0Kerbal?
2. If you want "old version" with all the parts you could get, go to CurseForge > scroll down to recent files > download the SpaceY-Lifters-1.17.1.zip > put the SpaceY-Lifters folder into the GameData folder.
The old version works with the KSP 1.12.5 no problem.