Hi !
I am trying to spawn a particle_fx node and activate it instantly, but something dosen’t work and I can’t figure what is wrong
local fdb = gui.new_particlefx_node(message.position,hash("hit_feedback"))
particlefx.play(fdb)
The “hit_feedback” particle_fx is in the UI file as needed
When I try to print fdb I get "unknown@(15.1321561,15.561561515,0)
So I guess the node has failed being created
When you say
it’s usually good to write what is going wrong (in this case, the effect does not start). In this case it’s deducible, that it’s the case, but in general it will be easier to track the error if we know what the expected behavior is, and what behavior you are receiving instead! 
Now, to the point: one error is that you are calling
particlefx.play(fdb)
instead of
gui.play_particlefx(fdp)
Does it work if you change it to this?
Yes thank you very much !
Maybe it could be nice to write something about it in the particle FX reference, just one line to warn people about the fact that they must look at the GUI reference if they want to use particule FX into GUI 
Well, particlefx.play() always takes the URL of a particle emitter component as its argument, not a GUI node. I’d say the naming of gui.new_particlefx_node() - and its entry in the API reference - makes it clear enough that it creates a GUI node, rather than a particle emitter component. If the reader has found their way to the API reference, then I’d say this suffices, but if you feel it’s lacking, then perhaps it doesn’t!
Since I started to learn using Defold, the duality between the GUI and the collection environnement has always been a factor of confusion, I understand the logic you hilight but I couldn’t find it wihout your precious help 
The idea of sharing assets and behaviors between game objects and GUI nodes is wonderful but it makes the editor tricky to understand because the boundaries are blurred by big similarities and tiny differences 
That’s why I think it could be good to prevent confusion in the documentation by telling users that this or this feature can be used in GUI or GO and send users to the respective pages !
That’s a bit off topic so thank you again and may the bugs stay away from you 