"Tombstone" trophy didn't unlock after finishing campaign.

So I played the campaign now hard difficulty and completed the WHOLE campaign but the trophy "Tombstone" didn't unlock. (Which the trophy said in order to unlock it you need to beat the campaign on hard.) I checked online and it seems to be an ongoing issue and I seem to not be the only person running into this issue and people have tried all three endings and replaying the campaign all over again and it still didn't unlock for them. I personally tried replaying the last mission with no success. Please help me because this is literally the last trophy that I have to unlock for the game and it's frustrating to think I've wasted so much time trying to unlock this one last trophy. ☹️