You encountered the Bird Lady in the elevator. And she did something to it and it is not working!
If you haven't even been in the elevator yet, investigate Totel's office.
This is the low-spoiler guide for "The elevator is not working!" puzzle in Mutropolis. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.