Please try this method to play music from a USB Key:
1. Login to your NAS file control system
2. Create an index for your USB files (like a shortcut to the USB folder) in your NAS device's default Music folder.
You can find that folder in your MUZO App by going to My Music -> Home Disk Share -> [your NAS name] -> Music->By Folder-> [your USB folder name]
Currently, the iOS App DLNA implementation is not compatible with NAS devices' USB Key/Modem. This is a known bug our engineering team is working to resolve as soon as possible. Currently, you are able to stream from a USB Key/Modem using any Android device.