Niagara System spawn in cpp

Hi everyone,
I have been trying for several days to display a niagara system from a cpp class but I fail … What I do not understand is that the system displays fine when I test via “Play” (viewport) but when I “Launch” nothing … The strangest thing is that the system is displayed in “Launch” when I place it in the level via the editor (which rules out a problem with the LOD config I think), but as soon as I instantiate it in my cpp, then no more instances of this system are visible in “Launch” mode (but it still works fine in “Play”). Would anyone have the time and kindness to give me some support? any idea?