Hi,
I took another look at the issue and was able to get the red debug lines to draw after tampering with the settings some. I also tried it on OS 10.13.1 and had no issue getting them to appear. I have a few general questions as to what your settings are, however a repo project will probably be easier.
What is your Effector Location Space set to?
Is there an Effector Target set?
What are the Joint Target settings?
When you say your animations act the same, are you referring to only in the preview window?
To start debunking what is causing the issue/for the repro project, I would recommend keeping it simple and creating a clean project without all of the conditional transforms maybe as well as sending me the one with them. This will give a good starting point when check to i see if it is the Two Bone IK node itself. When I looked into it, I was only tampering the settings for the Two Bone IK node. See screenshot below but disregard the strange values/settings since I was changing everything to extremes to get more visible results/seeing if I could break it. Also, the image is using Windows, just so I could get a very rough comparison of results in order to get a better idea as to what I was looking for.
-Thank you