I can't change rank to rank b, my job is SM, after defeat Moonnight in dungeon, there is no more quest need to follows.. now I stuck in ML20, can't level up, just do daily quest everyday, although my MP full
First of all, you should make your own thread, not hijack someone else's. Specially one that is 11 months old.
Then... You should give more details when asking this kind of question. It's not like we have memorized all quests to know what is expected to happen in the questline.
If it's the quest I think... It shouldn't just disappear after killing Moonlight, as you have to turn the quest in with Al Darone in Yggdrasil's Garden. Make sure you don't have to loot something from Moonlight, and also make sure to enter the dungeon in Normal mode.