This error occurs if you use a different user name on your new computer, and you restored the data without using Backup/Restore Library function.
The error occurs because the location of Analysis files stored in rekordbox database and a setting file is old user's directory.
There are several ways to resolve this issue.
Option 1. Use same user name on your new computer.
Option 2. Use Backup and Restore Library function.
1. Backup rekordbox Library on your old computer. (File->Library->Backup Library)
Save backup data in the external drive.
2. Connect the external drive to your new computer.
3. Restore rekordbox Library on your new computer. (File->Library->Restore Library)
Select the backed up data saved at step 1.
Option 3. Delete rekordbox Setting file
Delete following rekordbox setting file.
*User Library is a hidden folder. You can access it with [Go] menu of Finder while holding [Option] key.
This is a hidden folder. To view the hidden folder, follow the instruction below.
Please note the settings in the Preferences, waveform and beatgrid will be missing if you delete rekordbox setting file.
You need to re-analyze tracks in the collection again.