[Ernesto Garza]

Hi Chris,
I had the same problem today and this is why and how I fixed. I hope this is not too late for you.
By default, the Remove Grain effect take noise samples from the first frame of the sequence; so if this first frame has no noise, the Remove Grain plugin seems to has no effect. In my case, the first clip of the secuence had a fade in from black, so my first frame was completely black, with no noise of course, and the Remove Grain did no adjusment.
To fix this, you need to change the “Source Frame” from the “Sampling” setting of the plugin, from “0” to any other frame that has a representative amount of noise in your sequence and that`s it. It is a simple thing but it took me a couple of hours to figure it out. I hope my experience can save some of you time, fellows, as many other threads had saved mine.