In some situations, Audio Unit plug-ins may not be automatically rescanned and validated by Logic Pro / Ableton Live / Pro Tools, which rely on the "AUvaltool" (Audio Units Validation Tool).
By following the steps below, you should be able to force a rescan for it to occur on the next opening of your preferred DAW :
- First, make sure to close Logic Pro / Ableton Live / Pro Tools
- In the Finder, choose Go > Go to Folder from the menu.
- Type ~/Library/Caches in the "Go to the folder" field.
- Press the "Go" button
- Make sure once inside this folder to delete the "com.apple.audiounits.cache" file.
- Make sure to also delete the "com.apple.audiounits.sandboxed.cache" file as well.
The next time you start Logic, the installed Audio Unit plug-ins will be rescanned, and Logic should then start normally.
In case the problems persist, make sure to also refer to the page below: https://support.apple.com/HT201199