Make sure when you name your song that it doesn't have any spaces in it, for example let's say you named your song Song Name.ogg this won't show up in Blockland. Instead you'll have to add underscores to replace any spaces to this name, for example Song_Name.ogg this will then show up in Blockland. Also your song loop can be longer than 30 seconds but make sure that the file size is less than 500 kb.