Unity version - 2020.3.17f1. I created downloaded post processing asset in package manager, new camera, new layer, added PP volume, PP layer and changed PP properties.
Do you have a separate empty game object with a post process volume component on it, and its layer = ‘PostProcessing’? On that volume, add your profile, add some effects and you should see something.
If not, carefully follow the instructions on this thread: Why isn’t post processing working
I have 2 objects: main cam and empty obj with PP volume.@Llama_w_2Ls.