FabFilter User Forum
Volcano 3 Midi Input on Envelope Generator Doesn't Work
I just recreated the bug with a different plugin, so it's an Ableton bug not yours.
Jason — Apr 26, 2022
Ableton indeed only provides MIDI to the first plug-in. To get MIDI to another plug-in, you can copy the MIDI you need to send, and put it on a separate MIDI track. You can route the output of this MIDI track to the input of the plug-in you want to use the MIDI in.
Ralph Verdult (FabFilter) — Apr 26, 2022
In Ableton, if you set the Enveloper Generator to Midi, it only works if it is the very first insert. If there is anything before it, including an instrument, it won't work.