Mac window shifts left and a Windows window appears when I start a Windows app

Since the latest upgrade my Mac has a strange behaviour. I am in iOS mode, I see the Mac top and bottom menu etc. I click on the (Windows) Outlook button in the icon bar at the bottom and the entire screen shifts left and a the Windows interface appears. I cannot go back to the Mac menu, Coherence Mode is greyed out. It's like the two machines are not integrated, but separate. How can I go back to the previous status, i.e. when I am in (Windows) Outlook, I still see the Mac icons at the bottom, and Coherence works?