1. Open you system registry editor (Go to Start > Search > type regedit and hit Enter key)
2. Locate the key below and change Type value to 1 (please refer to the screenshot)
HKEY_LOCAL_MACHINE\SOFTWARE\Autodesk\AutoCAD\R20.0\ACAD-E001\AdLM
3. Create client license file, LICPATH.lic file, in Notepad.
e.g.
SERVER yourServerNemeHere 000000000000
USE_SERVER
Note: change yourServerNemeHere to your actual network license server name.
4. Place LICPATH.lic file in C:\Program Files\Autodesk\AutoCAD 2015\ folder
Note: Please make sure that your LICPATH.lic file doesn't have hidden .txt extension.
Tip: Show Hide file name extensions
5. Start AutoACAD 2015