Hello
The docking station is not detected at all by either computer (Windows and Mac) and you do not hear the connection jingle when you connect it?
About the service tag Dell docking stations like TB16, TB18DC, WD19, WD19TB, and WD19DC have a Service Tag or Express Service Code. Other Dell docking stations can be identified by technical support using the Dell order number - as per
Dell Support Page
The D6000 doesn't have service tag so I believe order number will be sufficient.