my cdj2000nexus connect error to the android rekordbox via usb

i have a problem  i trie to run rekordbox android to my cdj  but when i plug in my  phone  in usb i have galaxy S3  . phone lunch the  mtp  but nothing happend ! when i connect  to computer  all works fine ,  and wi-fi mode too . sry 4 bad english . pleaseee help :=()