Post upgrade to a new version of DLP, plugins configured with a custom script stop working.
Release : 15.8
When upgrading, the custom script isn't migrated to the correct new directory for the upgraded software. Likewise, the plugin configuration doesn't update automatically to look for the plugin in a different location.
Copy the plugin files to a known location with the appropriate permissions for the DLP service account to access it. Then you need to update the lookup plugin itself and point it to the correct location/file.