@Vaughanieee Ok. I went to the lab and left the walls up. There are 2 double glass paned doors on that level at each end of the corridor between the stairs and the lab room. I never noticed them before since you can't see them with the walls dropped.
You get no options on clicking on them. But you can see the lab with the plant displays, chemistry analyzer and the laptop. And most importantly, you can see the security doors to the mother plant room.
Clicking on the security door gives you the Use Keycard option. Clicking on the laptop gives you Hack. Clicking on the floor anywhere gets you the Go There option. I forgot to click on the chemistry lab but if memory serves me correctly, all you get at this point in the story are greyed out options. Didn't click on the plant displays either but I don't remember if that gives you any options. View maybe.
But to proceed in the story, you need to click on the security doors to the mother plant room and get the "Use Keycard" option and for the other sims, I used the group "Go Here Together" option to keep all the sims together for the next part of the story. My sims just ignored the base game doors and walked right in just like they would if they weren't there.
Hope this helps.