Possible reasons for a Playstation trophy not being rewarded?

Actually you don't really need to play veteran in one sitting it's just that the trophies glitch just replay all 3 levels or until you get the trophy also if you plan on playing zombies I would halt on that as there have been reports that you don't get the trophies if you play zombies this very thing happened to me tough on the mission the defector(which is a really hard mission due to the infinite spawns) had to play that same mission over and over until I got it so don't play zombies during your veteran run or your trophies will glitch