Is there anything in the folder ~/Library/Audio/Plug-Ins/Components (use Command+Shift+G in Finder to enter this file path)?
As far as I can tell, the error you're getting is produced by when the installer tries to relaunch macOS's registration app for Audio Units. The installer only tries to do this *after* it has installed the plugins, so if you restart your computer then your DAW should be able to detect them? Otherwise I'm not sure what's happening.