Since the Minx Xi was discontinued, Spotify have changed the way their service can be used and the Minx Xi can no longer support it.
Although it is still recognised as an available device, the Minx Xi 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 Minx Xi. Please note you do not need to log in on the Minx Xi.
To play Spotify content on your Minx Xi, please follow these steps:
1. When your device and the Minx xi are connected to the same network, open the Spotify App on your phone/tablet/laptop and select your desired media.
2. Connect to the Minx Xi using the Spotify 'speaker'/'Spotify Connect' icon.
3. Select the Minx Xi from the list of devices.
4. Once the Minx Xi has been selected, Spotify should begin playing from the Minx Xi.
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/