The Summon Durnehviir shout will only work when you do it in a large, flat, wide open space. You have to shout at the ground, not up in the air, and it may not work inside buildings or underground unless there is enough room. I've only ever used it outdoors. It is similar to a conjuration spell, which also has to be cast at the ground, not too far away. And make sure you hold down the shout button long enough to say all three words.
I play on the PS3 and I sometimes have problems with my Conjuration spells, where they won't work unless I'm casting them right in front of me, and only on very flat ground with a lot of room, and certain areas of the game don't seem to work for conjuring, at all. Like, all the way through Labyrinthian recently, my level 59 mage just couldn't seem to make them work at all. Sometimes if I save (make a hard save or manual save, not a quicksave or autosave), quit and then reload the save file, it fixes the problem, but not always.
Other than that, if you are on PC using any mods, it's possible that the mods are interfering with the regular game play in some way. Some mods are not compatible with each other, not compatible with the DLC, need a different load order, or should just be removed or deactivated.