Hey there. This week's mission is No Time Left, correct? Campaign missions can be played in one of two ways, - The campaign playlist on the Destination map lets you access any mission, and these can be Normal, or Legendary. Only playing them here, on Legendary (limited revives is the main modifier) counts for the triumph you have highlighted. - The other way is the weekly rotation of replayable campaign missions, on Advanced, Expert, or Master difficulty. The individual triumphs only count these; despite the 'any difficulty' wording, playing on Normal or Legendary does not count. So if you're playing No Time Left on Advanced, Expert or Master, it will not count towards the Lightfall - Legendary triumph. Also the two missions you've got marked off on this triumph, do not give you the individual mission triumphs, because the former are from the legendary playlist and the latter requires the weekly rotator mission.