panasonic nhzn-w60g SD problem

hello there,

I have 3rd gen Prius 2010 and it comes with the Japanese panasonic nhzn-w60g :

toyota.jp/manual/navi/nhzn-w60g_audio.pdf

the problem is when I insert the SDHC card t detects it but doesn't play the files!
it says : no files to play!
i tried different music formats and even formatting the sd card in different ways,,,,but all failed so far!

any advise?

the only way remained to play my music files is o burn DVD