Hi @jhj116,
Your issue looks similar to the one encountered in this thread - Can not load local Imagery with version 1.8.1
Can you try updating the plugin to the newest version available on the marketplace, or try using one of the pre-release builds linked by Kevin in the above thread?
When you say you have assigned three levels to a new layer, are you referring to the raster overlays that you added to the tileset? Your current sublevel should not impact which raster overlay is being used, but if you want to combine different raster overlays you can do so by editing the material.
-Alex