Your pacman.conf is the not the original provided by Mabox.
And was replaced probably by pacman.conf.pacnew during previous update - with your confirmation, it never happens automatically.
So remove it and replace with proper one.
sudo rm /etc/pacman.conf
sudo mv /etc/pacman-old.conf /etc/pacman.conf
Then get all updates, also from Mabox Linux repository:
yay