Today we released an update for the App Store version of Leech. This minor update changes the way Leech accesses the filesystem via the sandbox; the method we previously used didn’t work correctly in macOS Sierra, which is due out within a couple of weeks. (Because the direct version doesn’t use the sandbox, no update is required for direct customers.)
If you’re an App Store Leech user, please update to 3.3.1 before installing macOS Sierra. The update should be available now, or very shortly, via the App Store app.