revert to an older patch of CK2, idk which one yet but it's pretty much the only way to play the mod. It's completely broken on the latest version. Pretty sad, considering this mod is flat out better than the base game.

I figured it out i needed to link my steam and paradox. Thats the only way you can revert back to the version you v 2.8.3

In order to get the mod to work you need to roll CK2 back to 2.7.2
Normally you can't go further back than 3.0.1 so you have to follow these instructions from this post and you will be able to unlock earlier betas and be able to roll back to the required version.
Link to post - https://psteamcommunity.yuanyoumao.com/app/203770/discussions/0/1734339901253848647/

Hope this helps those that are stuck!

Rolled my game back to 2.7.2 but now the game won't start... Anyone have advice?