Aerender is a hack that wraps the entirely GUI based After Effects application with a basic command line render interface. The AE core itself still depends directly on the Window Manager.
You will not be able to run aerender from a render manager that is running as a service/daemon for this reason. (There are some hacks, like running with elevated privileges, that can band-aid a partial solution, but you will always run into a problem sooner or later, either trying to run multiple instances, or accessing some source asset, or something similar.)
If you run your render manager as a normal process, this goes away, because the normal process is running under the context of a user logged in to the console and thus these processes have access to the Window Manager.
Ive complained about this to AE many times, but I would not hold my breath expecting them to improve it any time soon.
Robin Scher | Uberware | 213.448.0443 | firstname.lastname@example.org | www.uberware.net
From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Greg Dickie
Sent: Friday, October 6, 2017 12:14 PM
Subject: [SSA-Discuss] aerender on OSX
This may be stupid question but it looks like aerender on OSX will not run because it cannot connect to the window manager. It's command line, isn't that the whole idea?
just a guy