Hi,
This is most likely due to not setting the -ObjC other linker flag in build settings, but in general to avoid difficulty it’s a better idea to use the tutorial to create a brand new app for RapidEars or other plugins than to add the plugins to OpenEars’ sample app, which is more oriented towards showing the features of stock OpenEars. It really only takes a few minutes and you’ll have an app customized for the specific use you want to make of it.