What isn't working, exactly? The Pie update moved some things around, and to do multi-window now you have to tap the Multitasking button and tap-and-hold on the app's icon (atop the preview) to launch it into multi-window mode or pop-up mode. If you use GoodLock with the Multitasking plug-in you get a few more options like tap-and-holding on the preview and dragging into split mode (you pick which side) or dragging into pop-up mode.