Why is my FMassActorFragment always a nullptr ?

Hello,
I started learning ECS and Unreal Engine Mass one month ago, I think that I have understand many things already. But my main problem remain unsolve, I would like find a way to get the actor attached ( by the mass agent component ). I tried many ways but at the end I my FMassActorFragment remain as a “nullptr”. Here’s my code :

Any solution, why is my Fragment not finding the Actor associated ?