This happens if Enjoyable is refused access to your input devices by Mac OS X. This usually happens if another application has requested exclusive access to them. Try quitting any other applications using your input devices. If that doesn't work, try disconnecting and reconnecting the device, then restarting Enjoyable. If it still doesn't work you may need to reboot.
Make sure it matches the name of the application exactly. If you still have trouble, name the mapping @Application and switch back to have Enjoyable try to deduce the correct name automatically.
This is a known issue with Cocoa applications, as they require more specially-crafted mouse events. We hope to fix it in a future version.