How to fix the restore down button not working
While working in Microsoft Windows, you may notice the restore down button or maximize button no longer works or is grayed out. When this happens, it's most likely because your Windows computer is running in Tablet mode. If you do not need Tablet mode, we suggest switching the computer back to desktop mode by following the steps in the following link.
If you enjoy using Tablet mode, try managing windows using the suggestions below.
How to manage windows in Tablet mode?
In Tablet mode, to open multiple windows, tap and hold down your finger on the window title bar instead of using the restore down button. While pressing down, drag your finger down until a small window appears with a bar in the middle. Choose which side of the screen you want the window to appear. For example, to open on the left side, drag the window to the left side of the bar. After releasing the window, if other windows are open, all available windows that can be shown are shown on the opposite side. Choose another window you want to appear on the opposite side.
After two windows are open and shown on the screen, to resize the windows drag the center bar to the left or right. If you want one of the windows to be full-screen again, drag the center bar to the edge of the screen.