Dear Sir,
Please try and see some kinds of several steps as below.
1. Get the latest rekordbox. (4.2.4 advanced5 : rev8937-10367-10385)
2. Run rekordbox, and open the preference dialog, and set [Preference]->[View]->[Waveform]->[Waveform Drawing Rate] to High / Medium again.
3. Turn off both rekordbox and RZX.
4. Reboot rekordbox first, and next, turn on the RZX.
5. Select except "Browse" on [Menu Bar]->[View] Deck mode.
If you still have never seen any waveform on RZX, please tell us more details on inquiry here.
Thanks,