Try entering these three commands: (to see if any of it is missing)
sudo apt-get -y install w32codecs ubuntu-restricted-extras
sudo apt-get -y install libdvdcss2 libdvdnav4 libdvdread4
sudo /usr/share/doc/libdvdread4/install-css.sh
UPDATE
If you don't already have Medibuntu (Ubuntu Media extras), then add that first:
Add repository
sudo wget
--output-document=/etc/apt/sources.list.d/medibuntu.list http://www.medibuntu.org/sources.list.d/$(lsb_release -cs).list &&
sudo apt-get --quiet update
(all on one line)
Add repository key
sudo apt-get --allow-unauthenticated install medibuntu-keyring
Update packages
sudo apt-get update && sudo apt-get -y upgrade
Update Software Center (with new media-apps)
sudo update-apt-xapian-index
(this may take 40+ seconds)