Maybe this is the reason.
JimStar wrote:After starting OctaneServer it will take some time before the LiveDB tree and LiveDB material previews will be available from Blender - as OctaneServer caches the LiveDB data from remote server right after starting. But only the materials groups tree will be re-cached every time after server start, LiveDB material preview images will be cached only once - so only the very first OctaneServer start will need some more time before LiveDB tree will be available in Blender.