A Trophy or an Achievement did not unlock in the game.
If you have a trophy or an achievement that did not unlock, double-check that you completed everything that needs to be accomplished in order to unlock the trophy or achievement. There are often several specific things that need to occur or be equipped for a trophy or achievement to unlock.
It may also be an issue of your Trophy or Achievements list not refreshing. Simply sign out of your PSN or Xbox account, start the game, and sign back in to your account when prompted from the main screen. Additionally, you can try signing into your console or system, then sign into your character and go to Settings > Log out of Destiny ('Change Profile' for Xbox One) and press start at the launch screen when prompted.
If you are sure that you have completed everything necessary and the trophy or achievement is still not unlocking, and refreshing your list did not solve the issue, you will need to retry the trophy or achievement. Unfortunately, there is no way for us to manually unlock trophies or achievements.
Networking or connection issues may delay the appearance of your trophy or achievement. If you don't see your trophy or achievement appear immediately, it may appear at a later date.