Accessed none error public variable

I’m having a really annoying issue with a -supposedly- very simple task that I just cannot find an answer for.
I have 2 blueprints; A character blueprint, and a HUD blueprint.
Within the HUD blueprint there is a boole variable that I want to access from the character blueprint.

Just for ease of example, say that if I press the “O” key (or any other key or event used to trigger) I want the boole variable within the HUD blueprint to become 1. So I create a reference variable within the character blueprint that refers to the HUD blueprint. Then give that variable a tooltip and make it public. Also the variable within the HUD blueprint is set to public.
No matter what I do, it never works. I always get the “Accessed None ‘HUD’ from node etc. etc.” error. This goes for any blueprint I create every time it wants to access a variable from another blueprint. Could someone show me how to do this?
I’ve already seen Direct Actor Communication Quick Start Guide | Unreal Engine Documentation but unfortunately it gives no help.

The Target Blueprint reference needs to be pointed to an actual reference in the world of the class. Currently the variable just points to the class type, allowing you to see the variables that belong to the class, but not an instance of the class in the game. In the case of a BP instance, not a HUD, in the world you could specify it via the variable input under the details section of the character BP for the Blueprint Target reference you have made like in that tutorial.

What I did was add the input key in FPS character class. This then sets the variable in the HUD. It could be reversed, but allowing multiple classes to call the “Set” seemed like a better option. I get the Player Controller and then “Get HUD” for that to actually get the HUD reference. Then simply set the variable I made public in the HUD.
In the HUD I simply draw the text from it’s publicly available variable.

You sir just saved me a very big headache. It worked, thanks a lot!