New "KeyNotFoundException" Errors - Unable to Fix

Hello!

I should preface this by saying that I’m new to using EventManager scripts and using Dictionaries to handle events. – For my c# class we’re recreating Atari Breakout, and I’m using dictionaries to use events invokers/listeners. Once I implemented them, the Unity Editor (2019.3.0B7) is giving me a dozen or so errors similar to the following:

KeyNotFoundException: The given key was not present in the dictionary.
System.Collections.Generic.Dictionary2[TKey,TValue].get_Item (TKey key) (at <437ba245d8404784b9fbab9b439ac908>:0)*</strong> __*EventManager.AddListener (EventName eventName, UnityEngine.Events.UnityAction1[T0] listener) (at Assets/Scripts/Events/EventManager.cs:159)__
HUD.Start () (at Assets/Scripts/HUD.cs:21)

I’ve combed through my code and my teachers similar code and can’t find anything I did wrong to throw these errors. They throw the error at every single AddInvoker or AddListener in their respective scripts. I don’t know if I’m personally missing something in my scripts, or if this is a bug in the editor. That’s where I need help. I’ve seen a few threads with KeyNotFoundException errors in which it was determined to be a bug in 2017 versions, but I’m using 2019.3.0B7 as mentioned above.

Screenshot attached for reference.

Looking for input asap!

Please see attached file for screenshot.