If you don’t see your Layers in your rigged model, check if you are in Preview mode.

The ability to pose or animate this mesh is available under ZSphere_1 subtool.

Let’s click on it.

After clicking on ZSphere_1, there is still no active Layers visible because

the model is still under Adaptive Skin preview mode.

Under Adaptive Skin preview mode, I can’t unbind mesh too.

Go under Adaptive Skin tab and toggle off Preview mode or press A.

Go under Rigging to unbind mesh to separate the rig and the mesh.

Then when you go under Layers, you will see

the previously recorded layer Arm and layer Legs.