Good evening MysticTeacup.
Short answer the scene scale in 3dcoat imports the model very tiny and in order to sculpt on a new voxel layer you need to create a mesh or import one onto that layer. There are different ways to do it, import another obj, use the models, primitives, splines, clone, tools etc. 3D coat will try to sculpt on the layer your pens geometry is touching, if you don't have geometry data for that layer on the current layer it will switch to the layer where there is geometry it can see. (Sorry if that sounded convoluted.) I have attached a startup file, just open it and import the object file into the voxel room. Your model should import at a resolution of 1,019,857 or thereabout, without having to scale anything. Create a new layer, and that object should also have sufficient resolution to sculpt on. 3dcoat is strange. the density of the voxels is tied to scale and the resolution. I copied the method mentioned by digman in this post
3Dcoat was importing the model very small, and for any new layers you you would have had to add a high resolution to even be able to maintain the shape and actually sculpt reasonably. You can test this out if you just add a new layer and add a model to the scene and scale it down and look at the "estimated poly count" and try to add it. It will appear deformed due to not having enough voxels and it will not sculpt correctly.
Hopefully this helps, let me know if it doesn't.