Something is wrong with compressor

I tried out the Cubase 8 compressor today and while I can hear a difference when twisting the knobs, I don’t see anything in the in, gr, and out meters on it. Once in a while they light up with something and it sticks there for like 10 seconds. My snare is only about 1 second long, if that.

What’s the deal? I am not sure if they are working like they should at all.