Delete old sync files
sudo rm /var/lib/pacman/sync/*
Re init pacman-key
sudo pacman-key --init
Populate key
sudo pacman-key --populate
Re sync
sudo pacman -Syyy
Now you can update successfully!
sudo rm /var/lib/pacman/sync/*
sudo pacman-key --init
sudo pacman-key --populate
sudo pacman -Syyy
Now you can update successfully!