Can't make two blueprints communicate

So, I’m trying to make an event trigger when I press a key, which is the “Toggle_Follow”, from the player character and run the “Is Follow” in the AI_Controller. But I always get the same error and nothing happens.

What’s the error and what does your code look like?

I edit them in. For some reason, it didn’t upload the first time

The error indicates that the Robot Cont Ref variable is empty or points to a destroyed object.
First add Invalid node becord doing anything with it, to keep your code from throwing errors if it is empty or points to invalid reference.
Next you must make sure that variable is getting set to a valid object before it is need by the code you have shown.
Can you show code where you have set the value of that variable?

It’s an Object Reference variable type, you can see it in the third image. And the AI Robot that is controlled by that controller is also set in the scene

the Obeject reference must be set , where did u set it? , its null based on the error given