These are unique to the specific computer where the software is installed. If you move the software to a new machine, your old activation code will not work; you must generate a new Request Code from the new machine first.
If you already have a code and are at the activation screen: i have an activation code from autodesk 2015
Tell me when you enter the activation code — for example: These are unique to the specific computer where
OR
It sounds like you may be looking for a related to using an activation code for AutoCAD / Autodesk 2015 — but I should give you a helpful heads-up first: i have an activation code from autodesk 2015