No Thumbnail for pic, video and music

I've installed Serviio 1.4 on Sabayon Linux.
Streamig ok, but there are no thumbnails for pics, and no cover for video and music, this happens on MediaBrowser on Linux and Win7, ServiiGo and BubbleUPNP on android and MediaMonkey on Win7.
On Metadata tab i've fagged correct voices.
What can i do?

I would check the Serviio logs... maybe there's a firewall blocking access to the Internet databases? Don't know about the pic thumbnails though

[DenyAll]

Also check that you've selected Retrieve Metadata for each of your shared folders on the Status tab in Serviio Console (that the checkbox under the M symbol is ticked).

No firewall blocking connections. I've installed serviio on a win7 pc and with the same configuration under metadata tab i have all thumbnail ok, but not on serviio on sabayon linux...