Mac Unlock

I'm new to TeamViewer but I've read the manual searched the community forums and haven't found the answer to my question/problem. I can't get TV to show the unlock screen on a mac that is still awake but locked. I have successfully connected to the machine because I see it's screen. However, all that I see is the blank screen with the default apple screen saver that has the computer name and the apple logo. This is what I see:

Key presses and mouse clicks have no effect. How do I get the computer to accept a log in?