You can face this message in Spark even if you are not trying to play the Radio service. This message is due to lack of responsiveness on our Radio service when Spark is trying to check if the service is available.
Even if this message is appearing, the Radio service is playable on your Phantom, it's just an alert that the service is not responding as expected.
Note: This issue have been fixed with the firmware 188.8.131.52 and with Spark version 1.6.2, if you want to check out what other bugs have been fixed with this release, please refer to the knowledge base article here
Products: Phantom | Version: 1.7.1 firmware
Setup: Solo, Duo or Mutli-room | Source type: Radio
Creation date: 08/07/2016 | KB article ID: SP0201
Update: 30/08/2016 | article version: 1.1