Petrenkov Door Glitch?

I'm at the beginning of AlternativA. I was told by a guy in the Warehouse to look for Prof. Pretenkov. I go there and cannot do anything at the door to his apartment. The cursor does not show any way of action, I can only click at the door, he says the name of professor and that's it. Any help???

Forget about this post. I manage to finaly find a "doorbell" next to the door. As I was standing in front of the door, I couldn't see it. Mods, you can delete this thread.