For Mac:
1) Launch Live, go to 'Live -> Preferences -> File Folder'
2) Make sure that 'Use Audio Units' and 'Use VST Plug-in System Folders' are turned on.
3) If the steps above are not working, please try re-scanning for it again by clicking 'Re-scan Plug-ins'
For Windows:
1) Launch Live, go to 'Options -> Preferences -> File Folder'
2) Make sure that 'Use VST Plug-in System Folders' are turned on.
3) Make sure the correct location is chosen under the VST Plug-in Custom Folder option. The location of the plug-in files depend on the location setting made during installation. The default locations are as below:
64-bits - C:\Program Files\VST Plugins
4) If the steps above are not working, please try re-scanning for it again by clicking 'Re-scan Plug-ins'