I actually got that error too, with the reason that my version of the main game was v19.x.OK, apparently this revised hint message is not clear enough.
You are trying to use an outdated game with the current version of the mod. Either download the appropriate mod for your game version (found in the first post of my thread under "Older Versions" -- not recommended), or update your game to the newest version 0.20.7.
I had just copied over the new 20.7.
What made it work was that I deleted compiled .py files (.pyc) which forced the game to re-compile them.
I suggest you build in a tool to remove any compiled python files that have uncompiled sources