Is the problem fixed?

My first thought was to simply stretch the browser window sideways to the right via the bottom right-corner until you can see the page options top-right of the browser window. This seemed too simple to suggest and might not be the problem.

There is a chance you opened a web-page or perhaps a pop-up window, or used the browser's built-in ability to view images and due to the image's presets, it forced your browser window to shrink in size and this somehow affected the default sizing of the window. Browsers often stick to the previously used page-size dimensions (and positioning on screen.)