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)
SERVER yourServerNemeHere 000000000000
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.
5. Start AutoACAD 2015