remote file didn't get replace

I have a automated synchronization set up via this script:

open CSVFTP
synchronize remote "C:\Sync" "/"
exit

This script was run with:
"C:\Program Files\WinSCP\WinSCP.exe" /script="C:\ftp_auto.txt"

However, if the remote file already got a file with the same name as the local, the file will not get ftp up even if the local one is newer. How can I upload and replace the files on the remote directory regardless?

Thanks.

AL

If you login to GUI, do you actually see the local file having newer timestamp than the remote one?