I want to buy a rekordbox 5 license key

rekordbox 5 is old and obsolete version for which support has stopped. 

So there are no license keys available for sale anymore. 

You would need to use rekordbox 6 or 7, which work with hardware unlock devices or paid plans. 

I have licenses for v5 but it won't do you any good. The servers that managed the licensing before v6 were taken offline permanently years ago. Rekordbox 5 will NOT start up if it wasn't 'activated' before those servers went offline.

To com minha DDJ-RB parada ,tenho a licença , mais como foi formatado o pc e não lembro do email antigo , ta parada a anos aqui, super errado isso que fizeram com o software.