Some other words from the interwebz:
Force Rescan in Plugin Manager:
1 Open the Plug-in Manager in your DAW (e.g., in Logic Pro, go to Logic Pro > Settings or Preferences > Plug-in Manager).
2 Locate the plugin that failed validation.
3 Select the plugin in the list, then click Reset & Rescan Selection.
Clear AU Cache: Manually deleting the AU cache file can force a complete new scan.
1 Close your DAW.
2 In Finder, click the Go menu, hold down the Option key, and select Library.
3 Navigate to ~/Library/Caches/AudioUnitCache/.
4 Delete the com.apple.audiounits.cache file. You might also want to remove ~/Library/Preferences/com.apple.audio.InfoHelper.plist.
5 Restart your computer (mandatory after this step).
Check Permissions and Installation: Ensure the plugin files in Macintosh HD/Library/Audio/Plug-Ins/Components have the correct permissions. Incorrect permissions can cause validation failures. You may need to grant Full Disk Access to your DAW and plugin manufacturer applications in System Settings.