Maximize / Minimize button missing

Support.com

1-833-202-2695

What to do when these 2 buttons are missing? I experienced this today while uploading a pic from desktop to pinterest. The window suddenly became full size – don’t know how – and then it wasn’t showing the maximize / minimize buttons. Only showing the close window button. Image attached.

However, the file explorer window in the taskbar is fine, showing all buttons.

Support.com Number