If you've recently updated to a new computer and migrated your data, you may have brought the rekordbox database into a new username and found that things don't work quite right. With a mismatched username in the settings file, a change needs to be made. Please follow these instructions to update your settings file for restored rekordbox functionality.
First things first, close rekordbox.
Next, you need know what your username is. You can find it by opening the System Preferences > Users & Groups applet.
If you need to, click the lock icon at the bottom to unlock the panel so you can make changes. Hold the control key while you click on your username from the list and select Advanced Options... and you'll see this window. Your username is here:
DO NOT change anything! Once you know your username, click Cancel.
Open a Finder window and go to the menu Go > Go to Folder... and in that window, copy/paste this:
Right-click on the rekordbox3.settings file and select Open with... and select Text Edit.
Before you make any changes, open the Text Edit Preferences and make sure you disable the Smart Quotes, then click the red ball to close the preferences.
Next, use the Find to locate these lines:
If they don't exist, that's fine - you should have the top two, at the very least.
In that line, it will have a val and the data for that will be the path to your OLD user's files; you need to update that. For example:
<VALUE name="pioneerDirectory" val="/Users/PulseOLD/Library/Pioneer/rekordbox"/>
<VALUE name="pioneerDirectory" val="/Users/Pulse/Library/Pioneer/rekordbox"/>
Once you've made the changes, save the file, then re-open rekordbox. You should be good to go! If you need additional support, please post in the forums or file a rekordbox support inquiry.