000680 : At least one layer must be selected.
You see this error message when the layer list is empty or when you do not select at least one layer in the layer list while creating a multilayer cache.
Select at least one layer in the layer list before you click OK to generate, update, or delete the cache. If the layer list is empty, make sure your map service is running and you can draw the service. Most often you see an empty layer list if your SOC machines cannot access the data referencing the layers in your map document.