Hey, we’ve been seeing some reports of this problem, following the below steps seem to fix it:

1. Close Logic Pro X
2. Make sure Finder is the active application
3. While holding the Option key, click on the Go menu at the top of your screen and select Library
4. Delete the following files from your User Library, if they are present:
   1. ~/Library/Caches/com.apple.audiounits.cache
   2. The contents of ~/Library/Caches/AudioUnitCache/
   3. ~/Library/Preferences/com.apple.audio.InfoHelper.plist
   4. ~/Library/Preferences/com.apple.audio.SandboxHelper.plist
5. Then, open a Terminal window (Applications -> Utilities -> Terminal), and enter the following commands (type each command and press “Enter” afterwards)
   1. killall -9 cfprefsd
   2. killall -9 AudioComponentRegistrar
6. Restart Logic Pro X