Getting stems to activate on Denon Prime 4.
Install 4.2.1 on desktop (and 4.2 P4), scan stems for any song you want, or folders, (this takes quite a while, about 30 seconds per song (register your profile on inmusic and your P4. With wifi, log in to your P4 (only once) then you can use the tracks marked with the stems symbol, by pressing the Hotcue button twice, the parameter buttons have very convenient shortcuts to turn on and off the acapella and instrumental.
Some more info would be nice …
Use current versions of Engine DJ and Engine OS.
Check if your licence shows up on your InMusic page, it should be listed as Engine DJ Stems. If it is not there, did you use the same email address when you purchased the licence? If it is different, the licence may not show up … in that case, contact support, they can add the missing licence to your InMusic account.
Then log in on your Prime 4 with your Engine DJ profile, this is important. The unit will probably tell you in a pop-up that stems are now available and ask for a reboot, hit “Got it!” and reboot … export some files with stems rendered to a USB stick with the Sync manager. On the Prime 4 hit the Hot Cue or Cue Button, maybe twice, and you should get 4 pads for stems control.