Hey there. Your Warlock has a successful Legend run, but there are 10 players in the roster, meaning people left and others joined - https://www.bungie.net/en/PGCR/9736434864?character=2305843009300176595 For any triumph that limits the number of players, it is not enough to only have that amount at the end of the activity. For example it is not possible for three players to get through a dungeon and for two to orbit just before the end, this does not qualify the remaining player for a solo completion. So even if you started with 4, and ended with 4, and never once exceeded four, even having a single player leaving and being replaced will still mean there were 5 players involved, or more, depending on how many get replaced. For that triumph if you replace a player, you need to return to orbit and relaunch it.