Loading a track with no Beatgrid will disable Sync for that deck.
A Beatgrid will be created for un-analyzed tracks if ‘Analyze BPM / Beatgrid’ is enabled in the Analysis settings.
Once a Beatgrid has been created you can then press Sync to engage Beat Sync.
If ‘Analyze BPM / Beatgrid’ is not enabled in the Analysis settings, Sync will not be available for that track.
If a track has previously been analyzed, but has no Beatgrid, then Serato DJ will not create a new Beatgrid for that track.
TIP: Manually add a Beatgrid for tracks to enable Sync functionality for that deck.