Could be that Windows misaligned the placement of the window (this happens to me from time to time)
Shift+Right click on the taskbar icon for
draw.io, and you should get options with "move", "maximize", etc to show up. Try Maximize to see if that helps. Move may also work but microsoft's implementation of that function is finicky -- need to click Move, then tap an arrow key on your keyboard, then the window should attach to your mouse, then click the mouse to set it down once it's in a spot you can interact with the buttons on the bar.