Have you tried disabling the firewall in macOS?
I can't drag song into players when using Rekordbox
I have a 2 Pioneer CDJ-2000Nxs and a DJM-200nxs (1st gen). I have the latest firmware on my players and latest version of rekordbox. My music is on an external Lacie drive which I've used for a few years without problems.
I just upgraded my Max OS to Catalina but it appears there should not be any issues based on the latest updates. I don't use music from iTunes/Music. Now when I have my Pro-DJ-Link on and see my mixer and two cdjs I cannot for the life of me get any songs loaded into Rekordbox.
I can read music from USB or SD card directly connected to the player. I tried doing the same with music on my computer instead of the external drive and that doesn't work.
Any suggestions would be appreciated.