Re: Help!! I have all the letters but it says I don’t have one and no weapon unlock

That does sound familiar though. Do check out if this fix works for you:

1. Export the game save files to an USB drive.
2. Delete the game save files in the console.
3. Start the game. You'll have to adjust contrast and play again the intro.
4. Now, play the War Story and complete the bugged challenge. It will show correctly achieved.
5. Close the game, and restore the game save files from the USB to the console.
6. Start the game, and you'll have your reward at the armory.

hope this works for you, XP appreciated + accept it as solution if it works, thanks