I think the Devs and others could help you better if you give a few more details. does VLC give any error messages.. they have a log somewhere itcould give ideas on whether a certain codec pack etc need installingdoes it show anything when you try like fuzzy pics or just stay black.have you tried running VLC from a terminal as that may give you some errors The more Info you can give the quicker and easier it will be to correct your issue.
you "have" enabled dvd playback by installing the extra files needed yes ?
Unlike the 'buntu side.. debian is a bit harder to get dvd's to play on especially encrypted ones...although both require libdvdread4 and libdvdcss2 to be installed as extras.. deb has a different method.https://wiki.debian.org/CDDVDplease note any links are only for informational purposes and are used at owners sole risk.
sudo apt-get install libdvdread4
sudo leafpad /etc/apt/sources.list
deb http://download.videolan.org/pub/debian/stable/ /deb-src http://download.videolan.org/pub/debian/stable/ /
wget -O - http://download.videolan.org/pub/debian/videolan-apt.asc|sudo apt-key add -
you need libdvdcss2 also ... as per my post