There has been some problems with being unable to finish this quest due to bugs/glitches. I stumbled on one that has yet to have a fix, but I may have figured out a trick to it.
The bug is after you defeat Serge the sentry bot. Ronnie may glitch pass the door making her unable to unlock the terminal. I managed to fix this, but requires to be far enough into the story.
*** Spoiler - click to reveal ***you have you have to join the institute and get their synth spawn grenades. Once you have those you want to throw some at her from the hallway gap before Serge. basically you want them to move Ronnie so she is no longer stuck by the door. Once she starts fighting the synths, re-load the area then sit by the chair and wait for Ronnie to kill the remaining synths. Then she'll make a comment about serge and "should" appear in front of the terminal.