The question is, what is your midi clip driving?
By itself, Midi is not audio (it's just data) and will not generate any sound until it's connected to an audio track.
If you're driving an external synth you'll need to record the AUDIO from the synth to apply clip based Fx.
If you're driving a soft synth you need to either bounce to track or preferably freeze the synth, then apply clip based Fx.