First make sure you have followed the steps in in Migrate DbVisualizer settings to new environment.
- The location for the license file is listed in DbVisualizer Pro, license file location
- Copy the dbvis.license file from the old machine to the Download folder on your new machine
- Start DbVisualizer on your new machine and open Help->License Key
- Select the dbvis.license file in your Download folder
- Re-start DbVisualizer when prompted
- Remove the dbvis.license file in the old machine