I have installed the latest versions of the KORG Collection plugins on my late 2015 MacBook Pro running MacOS 10.15 Catalina. Only the PolySix shows up in my list of plugins in Cubase 10.5 and 11. The instruments do appear in Presonus Studio One v4.5 (as both AU and VST2 plugins) and run without any problems. So the problem is not with the plugins themselves.
Has anyone else been able to successfully install all of the KORG Collection instruments in Cubase 11 (so that the plugins appear in the VST Instrument Rack)?