Box Sync 4.0 provides detailed user notifications if there an issue syncing a file or folder.
You can only sync new uploads of Mac packages. The Mac package support provided by Box allows collaborators to download packages correctly. Any package uploaded to Box (using the upload folder method provided by some browsers) prior to the release of this feature will no longer sync automatically.
Follow this sequence to workaround this problem:
Quit Box Sync.
Save a backup of your package to a local directory outside of your Box Sync folder
Delete the package from your original Box location.
Start Box Sync and wait until your files are synced.
Move the backup of your package (Step 2) back into your Box Sync folder