@Titus > Chances are you have migrated the database from another computer to this new one and didn't use the same username on both machines, thus creating a hiccup in the settings file looking for the database in a folder that doesn't exist. You can edit the settings file to change this, but I'll need a bit of info before providing you the instructions.
Can you tell me which folder is listed in rekordbox under Preferences > Analysis > Track Analysis > "PIONEER" folder
I also need you to open the finder and press Shift + Command + G and enter: ~/Library/Pioneer/rekordbox
Next, press Command + I and look under "Where" in the info box and write what it says here.