Hi Paul
Unfortunately none of your suggestions work! When in Logic Pro X, when I scroll down to useable plug-ins (Vienna Ensemble being the only independent plug-in I have purchased), all I see under AU instruments is Apple and no Vienna. When trying to load Vienna Ensemble (64-bit) direct from Applications folder all I get is the same error message as in previous post to you:
Check with the developer to make sure Vienna Ensemble (64-bit) works with this version of macOS. You may need to reinstall the application. Be sure to install any available updates for the application and macOS. Click Report to see more detailed information and send a report to Apple.
Kevin