This literally means that there is no data to optimize.
The plugin is not saving BitData as it takes too much space in ram and harddisk.
But bit data is automatically generated when you load data from some file ( press [Load Data] )
Here are the save files.[It was in description. Download and Extract into (D:) ]
You could also regenerate the whole map if you want. Look at the youtube video.
Also please check every value when creating/adding new LevelBlockConstructor. LevelSize, LevelHeight, BlockMesh, BlockMaterial etc.]
You can create a Blueprint prefab with those value and drag and drop them into level.
Good Luck.
I also recompiled the whole engine and plugin as Engine Plugin.