Sync manager broken

I have a problem with syncing info such as cue points and track color from a device to my local rekordbox library. I have done this hundreds of times before but it stopped working today.

- I opened Rekordbox.
- I plugged in my device.
- I went to Sync Manager.
- I pushed Cue grid info.
- Progression bar appeared and disappeared (it took some time).
- I checked my playlist in the local library and nothing had changed. The track info is usually synced after the progression bar is gone.

I also checked the playlist in my device to make sure that the changes I made before (on my laptop) was still there and they were. The sync feature of rekordbox was just broken. How can this be solved? Thanks.