I already contacted support about the issue and they told be to use the SDK forum to get in contact with the development team about this issue. The issue is that R21 cannot be used any more within a background deamon(service) on macOS. One of our customers just switched to R21 for their upcoming project and they got into that issue.
If you need help to reproduce the issue or a test machine (teamviewer) to test something, please let me know.
Or if you have any test application/ test version you would like me to run, let me know as well.
Perhaps a version that prints every step helps you to find the location/module that is responsible.
E.g. Loading module "asdsdas" now, Initializing "asdsdsa".
About running as background deamon(service):
Many companies require security rules like that everyone has to logout if they leave or that the user logged-in is not allowed to access all projects that the render farm can access. Therefore the render farm has to run as background service/deamon. I was already told by support "I would not be aware that our software can even be used without a logged-in user". BUT: Even if you have not tested it, companies use it and HAVE TO use it.
I can not tell you the exact issue why R21 does not run, I have just collected some issues I found.
BUT: these errors have been printed by R20 as well, but R20 rendered anyway.
The last message that is printed is "LLVM Profile Error: Failed to write file 'default.profraw': Permission denied".
R20 prints the same message when the app is closed (after the render).
There is an other issue with the file as well, customers report that these files are big and if you use Arnold, they are saved beside the scene. Solidangle (Arnold renderer) has already told me that the issue of that file is in the C4D python lib: "The default.profraw file is created in the current working directory when Cinema 4D starts and written when Cinema 4D closes."
If the mac was restarted and nobody ever logged in, then the last error is
_RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
2020-02-06 15:08:36.947 Commandline[477:3391] +[NSXPCSharedListener endpointForReply:withListenerName:]: an error occurred while attempting to obtain endpoint for listener 'ClientCallsAuxiliary': Connection interrupted
The Commandline app tries to load many libs that require an UI. Shouldn't the Commandline app be able to run without UI libs? It prints about 150.000 bytes of warning messages each time started.
net.maxon.gui: Initialization of mac_clipboard.mm [initialization] failed.
net.maxon.c4d.nbp: nimbus_impl.cpp could not be initialized because net.maxon.interface.amemulation is missing.
net.maxon.c4d.nodeeditor_material: could not be initialized because net.maxon.mvp.windowclasses.base is missing.