Hi, I finished the first mission with the scientists the one with kabutops and I beat the timeless trainers and taen however when i go to the lab none of the scientists activate a mission.
You have to defeat Reukra (I think that was his name, Perfectionist leader) in Void Gauntlet. After that he leaves and never come back. Once done head to Perfectionist base (under the Jade tower). There should be full of investigators. They are turning all place upside-down and also have unlocked doors to said cell with books and also to basement with one special pokemon.
EDIT: And one more thing. To activate this quest you have to go to Perfectionist Base and read a note first (it should be where you battled Zygarde guy first time)