Noise Gate Plugin Won't Click

Using Garageband 10.1 I'm trying to record a narration for a video. The noise gate is not clickable, see attached screenshot.

I can't get the noise gate to work, so finally I got down to trying to LOAD a plugin after scouring the forums here. Unfortunately I have no plugin in the folder! I would assume these plugins came with the original download, but apparently not or I must have done something wrong somehow. How do I get the plugin installed, where do I get it?

Thanks so much!