I've been using the demo version of Serum on my mac for GarageBand and its always worked fine. However, with the new High Sierra update, I keep getting a message saying that 'Audio Unit plug-in can't be used' and 'The Audio Unit “Serum” could not be loaded for your project, and may need to be updated.' whenever I load a project or try to initialize a new instance of Serum. What needs to be fixed?