Why does Plex not play an Album that has been doesnloaded

I have just walked home from the pub expecting an album to play 1->12 as downloaded to plex client when it gets to song 9 then tries network connections fails and fails to play anything else, this is not what I have paid for. what is going on? I have downloaded the full album through plex, I expect the full album to play else I would stick with itunes. If I look at plex it shows the next track as if ready to play but it should have continued without interruption? What is the bug?