I bought a new laptop and want to use my existing license for Pro 2 and then pay the upgrade to Pro 4. How do I do this?
To install Ttraktor Pro 4 on your new laptop you need to use Native Access connected to your account. I don't think you can upgrade from TP 2 to TP 4, so you will have to buy TP 4, or the light version, Traktor Play.
Traktor Pro 2 will not work on modern Mac OS as far as I know. Traktor Play is rubbish, please don't buy that. It only supports like 4 controllers.
Best bet is to upgrade to 4.
You can also try the demo if you are not sure yet. Just install Native Access.
If you want to transfer your old collection move over the data from ~/Documents/Native Instruments/Traktor 2.X.X. over to your new computer.
~/Documents/Native Instruments/Traktor 2.X.X