I can only refer you to the walkthrough for this problem (written and video walkthroughs).
Having said that, I have been reading the posts in the Hints forum here for a very long time now and your exact situation has come up many times, this situation where people are stuck in the lab and can't leave, receiving the same message that you do when they try.
Take a look, for example, at this thread from the Steam forum for the game:
stuck in the labUnless someone else comes along with a different idea, or a saved game, I really can't think of anything else to suggest, unfortunately.