DDJ RZX - Rekordbox - No videos on second screen

I have just installed my DDJ RZX and Rekordbox 4.3 on my laptop (Windows 10 - i7 6820Hk Quad Core 2.7 GHz - Ram 32GB) and when I want to put the external video output (HDMI Extended screen mode) there's a gray window without video image (I specify that I also use other video software before and that everything works correctly with them)