Official comment
Hey PB,
Sorry - changes to rekordbox in version 2 dropped the key requirement to use rekordbox in export mode. In version 4 when DJ mode was introduced, a key was required to activate the performance features. Unfortunately the key from v1 is not valid for any other version. With the release of v6, we have moved to a hardware unlock and subscription model, and discontinued the availability of v5 keys (although the software does continue to function if you have one).