Hold down the shout button for longer it takes a couple of seconds of holding it to trigger all three words, but there are a few Dragons that will resist (listed on the Bend Will page).
I have seen this issue before too, with me being level 80 with all main quests cleared. This has namely occured with me for blood dragons.
If you guys are playing on pc with mods, there are a few dragon mods that increase dragon magic resistance. For me, Deadly Dragons was the culprit. Check your mod settings if you have mods enabled.
I have the Xbox 360 edition so I can't really mod my games. I should be completing the full shout since it takes around two minutes to be able to shout again. I have had the glitch about 10 times with a blood dragon, twice with an ancient dragon, and a few times with a regular dragon.
You need Fortify magicka, so You need more Points. After i used a Trick to Push my entchanting to ridiculous Points, could i shouting a Dragon with Bend will and He dosen't resists anymore (i got an Ring with: "increases your Magicka by 447 points"
Sorry for my horrible english