I downloaded the newest version of JUCE5, and generated an empty new plugin project (default options, xcode exporter). The resultant Audio Unit plugin can be found by Logic Pro 9 (running in 64bit mode). But when an instance is generated , Logic clams like “failed to load plugin, please contact vendor” (I’m using a Chinese system and don’t know the exact English version of this error report).
My Mac OS X version is 10.12.4, and XCode version is 8.3.2.