How do we find sergio were stuck use the magnifying glass but nothing happens..

The magnifying glass can be tricky until you learn to use it. You want to go to the small set of stairs to the left of Anna's desk, with a red rug on them. Don't focus on the door, but point the magnifying glass away from the door where the tissues are and point it towards the stairs and the edge of the rug. When you are in the right place, a small icon will pop up in the lower right of your screen and then you will see the tissues (there is a small bell sound that will go off when you are in the right place also) Keep moving it around the stair and lower floor area until the tissues pop up. Once they do, you will be repeating the action over and over as you are basically taken on a tour of the the Chalet and it's immediate environs.