If it's disappeared from view and only shows up when you move your mouse to the bottom of your Monitor then you can unhide the Taskbar from the Taskbar Properties.

If it gone from view, place your mouse to the bottom edge. When you see it turns to a black arrow, Left -click and hold your mouse and drag it into view and then lock it.

If it's double height, unlock it and mouse over the top edge, Left-click hold and drag it down to single height and lock the taskbar.