Effect not working

[Carla Marie5FD0]

Hi, I had this message on one of my AE project and it is apparently because of the licence of the effect. But I don't understand why because i just downloaded the effect, plus I don't know how to check the licence. Can someone help me please? 

[Jose Panadero]

We need more info about that plugin.

It looks like a plugin for particles and probably it is Red Giant Trapcode Particular.  That red cross is obviously an indicator that you don't have a valid license.