It is definitely possible as Sims has said that you have enabled tablet mode, by going to the bottom right corner click the chat box icon, and make sure nothing is set to hidden, or tablet mode. This can really be your culprit in this situation. Also for more knowledge, dual screen setup is when you have two monitors set up side by side on the same computer, sometimes your computer detects a "Ghost Monitor" or a monitor that doesnt actually exist and set it by default on accident. The more you know!