Q: How do I “force” Logic Pro 8 to re-scan my Audio Units plug-ins?
A: Apple Logic Pro 8 validates (scans) plug-ins automatically when it is first opened, when it is updated, or when new Aplug-ins are installed or existing plug-ins are updated. You could “force” re-scanning by updating a plug-in or by adding a new plug-in.
To manually validate or activate plug-ins, go to Logic Pro > Preferences > Audio Units Manager. From this window, you can re-scan individual plug-ins, as well as activate individual plug-ins that failed validation (activate failed plug-ins at your own risk). You can also manually disable “failed” plug-ins or plug-ins you don’t want to use from this window.
BONUS TIP: If you hold down the Control and Shift keys while starting Logic Pro, only validated plug-ins will load and be available. Plug-ins that failed validation will be disabled.