RNS 310 - navigation has no sound

Hi guys,

I've recently bought a Skoda Ocatavia Break of 2010, which came with the RNS 310 Navigation System.
The seller had in it a original SD Card with the 2015 maps.
And the radio and mp3 player works great.

So far, so good.

The problem is that there is no navigation voice instruction. The navigation system works well, but no sound...only the radio sound come from the speaker.
In the sound menu I've already turn the navigation sound to the maximum, but nothing. I tried even to put the radio/media sound to zero, and put the navigation sound to the maximum, but equally no sound, no instruction. The GPS works well, I can see it on the console and behind the wheel, but no voice instruction where to turn, etc.

What could be the problem? Please help me!

Thanks for your help.

Greetings from Portugal,

HGS