Accessed None trying to read property, how to fix?

[Naiuma]

Hello,
I am trying to communicate between blueprints.
I have one BP called BP_Door_Greenhouse with a custom event called SimulatePhysics
Here is how it looks:

Then I have another blueprint where I created a variable called Boor_Physics which is referenced to the first blueprint. Then I call that Simulate Physics custom event with this varable.

But it says Accessed None trying to read property Door_Physics. Why? Just in case if it matters, there is only one blueprint in the scene called BP_Door_Greenhouse.

[ClockworkOcean]

You have to assign the reference.

Blueprints 108 - Direct Blueprint Communication

[Naiuma]

Cool! Thank you very mcuh for the tutorial.