Unable to sync on my android devices.

Hello Everyone,

I have a Plex Media Server installed don a centos 7, the server is reachable from outside, I can listen music when my devices are connected to internet, but I cannot sync, it start then say finished, but there is nothing being downloaded.

On the bottom of the screen, it say that there is no transcoding server available.

I check everything and it look good, I restart the PMS and check that the plex pass was applied.

Thank you in advance