I remember that Particles would be active if put it in Level Viewport in UE4Editor, but now these particles in scene all are unactive, is this a bug?
if your viewport is not set to realtime (CTRL + R) they might not play.
Im guessing that this is the issue.
No, I think it’s a bug, because when I use the newest version(v4.14) of UE4, Particles all are active.
doesnt make much sense since your original post also mentions you are using 4.14. and I use particles daily, and havent seen this issue yet.
honestly think it was a non-active viewport you where looking at.