Normally Humanoid 4 Sites will not work with playmaker because that is not part of Humanoid Control.
As Humanoid Sites are implemented using AssetBundles which do not support scripts, you cannot normally use Playmaker on your Humanoid Sites.
However, there is a workaround: you can make your own Visitor with Playmaker included. That visitor can then visit sites with Playmaker code. So as long as you make sure your visitors have this custom Visitor-with-Playmaker, it works.