I just spent a few hours trying to figure out why my Call Function node wasn't working.
The class name matched, no errors being thrown, copied the class name and the parameters right from the script.
It just wasn't working...
Then I realized I had a namespace for my public class.
So for those that don't know if you have a namespace for the class the class name field in any Function Node should be:
This was a total facepalm on my part but I hope this saves anyone some time if running into this issue.