The quest "From Within" won't start

[黑色行动]

So I built the teleporter with the help of the minutemen then went inside the institute, met father and completed institutionalize. After that, i went to the BoS HQ and speak to Elder Maxson, I believe im supposed to trigger the quest "From Within" in which i will find Doc li but all Maxson is saying is "Im too busy", "I'll send for you if i need you", etc. I have already finished "show no mercy" quest so im supposed to get the next quest.

Its as if i can't continue the BoS questline anymore, they're not hostile to me or anything. Did i mess something up?

[DEVOLVE MINHA CACHAÇA!]

Well, you didn't make it clear, so I'm asking: Are you already a BoS Paladin and did you clear Fort Strong during Show No Mercy?

From my understanding, there are some BoS quests prior to From Within that must be cimpleted to reach that point.

http://fallout.wikia.com/wiki/Fallout_4_quests#Brotherhood_of_Steel

[Void#151625]

1 check so all boss repeater quest are turned in and not taken
2 check so you far enough in both main story and bos story
3 check so you never loaded from contiune button( continue button will break travel points,quests and much more.)
4 empty after each run of Fallout 4 %tmp% to make sure you do not have old cache that creates data conflict, what could create bad refrence to old data that nolonger exists.
5 if you use mods make sure that they do not change quests! this can also break quests!
6. never change mods on an active safe!
7. allway start a new gameplay if you want to switch mods to make sure to prevent broken data links!
8 updated mods with no data removed are fine If an update mod removes refrences it will break the current save file. what will require you to start a new game to fix the broken references!