Mirror-check (what shows as red) checks if the mirror you use is syncing with the main mirror.
Pacman -Syy syncs your local database with the database of your used mirror.
I hope you see the difference between the 2....
It is known that since yesterday the default mirror is not syncing. Just use another mirror:
kdesu kate /etc/pacman.d/mirrorlist
Comment out the first used mirror (place a # in front of the Server = line of dacentec) and the next mirror listed will be used. Or make a mirror close to you the first uncommented.