Since the NP30 was discontinued, Spotify have changed the way their service can be used and the NP30 can no longer support it.
Although it is still recognised as an available device, the NP30 requires a manual login which Spotify no longer permit. Instead, you will need to use the Spotify Connect service.
First, you have to make sure you have a Spotify premium account so you are able to make use of Spotify Connect.
This enables you to stream connect wirelessly from the Spotify App straight to your NP30. Please note you do not need to log in on the NP30.
To play Spotify content on your NP30, please follow these steps:
1. When your device and the NP30 are connected to the same network, open the Spotify App on your phone/tablet/laptop and select your desired media.
2. Connect to the NP30 using the Spotify 'speaker'/'Spotify Connect' icon.
3. Select the NP30 from the list of devices.
4. Once the NP30 has been selected, Spotify should begin playing from the NP30.
For more information regarding how to use Spotify Connect, please follow this article here:
https://support.spotify.com/us/listen_everywhere/supported_connection_types/spotify-connect/