CustomEditor Not Working or Visible

I'm having an issue with CustomEditor's not actually showing.

I have a controller (MonoBehaviour) that has an array of Interaction attached to it. The Interaction class looks like:

 [Serializable]
 public class Interaction
 {
     public ConditionContainer[] Conditions;
 }

ConditionContainer is a way to wrap up and instantiate actual Conditions for an Interaction to occur (i.e. bumped into, press a key, etc).

 [Serializable]
 public class ConditionContainer : ScriptableObject
 { 
     public ConditionType ConditionType;

     public Condition Condition;

     public bool IsMet()
     {
         if( Condition != null )
         {
             return Condition.IsMet();
         }

         return true;
     }
 }

Condition itself is an abstract class and I was planning on instantiating it in my CustomEditor, based on the ConditionType that was set, and having CustomEditor's for each specific Condition (i.e. BumpedIntoCondition, PressedKeyCondition).

 [Serializable]
 public abstract class Condition
 {
     public ConditionType ConditionType;

     public virtual bool IsMet()
     {
         return true;
     }
 }

My CustomEditor's NEVER display or work. I don't know if it's because they don't play well with arrays or if I'm missing some kind of derivation or attribute or what.

Just trying to output a label that says "Hello World" fails...

 [CustomEditor(typeof(ConditionContainer), true)]
 [CanEditMultipleObjects]
 public class ConditionContainerEditor : Editor
 { 
     public override void OnInspectorGUI()
     {

         //serializedObject.Update(); 

         EditorGUILayout.LabelField("Hello World"); 

         //serializedObject.ApplyModifiedProperties();
     }
 }

Am I missing something? I've commented out the serializedObject details, but they don't make a difference either way. I've tried calling into the base.OnInspectorGUI() as well... No luck anywhere. The Editor itself is inside Assets\Editor -- when I open the code, it tosses it into another C# Project called "Editors" so I assume it's recognizing.

https://imgur.com/a/LnUgI

I'm using Unity 2017.3 Personal.