When in the Montage, it’s easy to miss that one of the plugins is off for that clip. There is a Specific Tool Window for Effects, but more often than not I have the Marker or something else shown in this area. I know now to always keep that on. If I had 3 effect Plugins, it would show 3 fx for that clip even though any one of them could be off. Some kind of visual reference would be helpful here. Even if you had 3 plugins setup and only 2 were being used, then it could show 2fx so you could have a quick visual reference. Just show the active plugin #'s.
p.s. The effect that was missing was a subtle change to the sound, so I did not notice it until now.