My Behavior Tree doesn't run


All things in my AI Controller class works. In the ai controller class, I have tested: AI character, behavior tree (referenced in ai enemy blueprint), BlackboardAsset, Behaviour Tree Component, Blackboard Component. All available, initialized and works. However, the real assets in the Content Browser (Behavior Tree and Blackboard) don’t work when I at runtime. I don’t understand. Earlier it worked, then stopped working, worked and don’t work now again. I just tried to create blueprint for my ai controller class and assigned it to the ai character blueprint - the behavior tree stopped working, so I referenced the C++ class of ai controller again (removing ai controlling blueprint), but it didn’t help.
My behavior tree doesn’t’ work. WTF?