As the first step, we recommend you to run a detailed channels scan and test the connection. This link will provide you with further information and steps to follow.
Even though this article is not intended to fix the audio issue, it will allow you to scan all the available channels one more time. This way, we will be able to determine if the issue is related to the signal you are getting or not.
it happens the same to me. In my case I'm in Spain and still trying to set up at home. I followed all the steps as described and the signal is good since when I connect a cable to the Tv, first connected to the sling box, the audio arrives to the Tv. For some reason the audio doesn't arrive online for some channels independently on if they are hd or not.
Waiting for some solution,
Thaks in advance