Talk:The Garden of Sinners Collaboration Event (US)/@comment-112.200.105.233-20180209050355/@comment-2607:FEA8:3100:2A2:FDB0:5FF4:9389:EBC3-20180209051547

Under the mission rewards tab, tap the tab next to "Completed Missions" and look under "In progress". You should be able to find out which quest you're missing and what it unlocks