Rekordbox not found on my left CDJ3000?

Correctly formatted SD-card used to export playlists from Rekordbox to this SD-card.

But when putting the SD-card in my left CDJ-3000 Player, I get the error-message

rekortdbox Database Not Found
For optimum performance, use rekordbox.

I can see the files and folders on the SD, but not with RB, but... when I correctly remove the SD-card and I put it in the right CDJ3000 of my set-up, the SD is read correctly and I can use all playlists and other sorting the same way I use any other USB-stick or laptop (Export mode)

Both CDJ3000's have the same latest firmware (v3.22) so what is happening here?