Deeker

Just got this ml350. It has the factory rear dvd player and head rest tv .I have a problem with it not playing all dvd .like kid dvds it will play .but any movies it won't read say not recognised disk.as far as I know this is a Canadian mb. Never left the country. Could this be a zone problem with the dvd player? Any ideas ? As well what is the w164 for the forum. Any help?
Thanks