Same here. Transferred to new iMac and got all my Toontrack products working, including SD3. But I never had done the Library part 3 and 4 installs (surrounds, etc). When I hit install I go through process and says and run the config, as others above.
Reply To: Can't install SD3 Library Part 1 on MacOS Catalina version: 3.1.5 Operating system: macOS Catalina (10.15)