How to display the window size as the size is changed by Resizer?

Thank you for the reply. 

I went into the Settings menu and confirmed that the option you mentioned had already been unchecked.. So I reinstalled the extension but ended up with no indication of the window size still.

I'm quite sure that the grey pop-up indicating a window size used to display on the right bottom corner of my Chrome browser window when resizing the browser window, but now it will not show even though I'm resizing the browser window manually.

I've viewed the screenshot too but don't have a clue about what else I can try.
If there is other possible troubleshooting, please let me know.  

I've just noticed that the window size popup is showing in the tabs I've newly opened after the reinstall, meaning that the reinstall has fixed the issue.

Yes, I forgot to mention that it won't work on pages you opened before installing the extension or on pages you opened before changing that setting, without refreshing them. The code needed to display that popup is loaded when the page loads so, if the tooltip is disabled, it won't load at all, even if you enable it, unless you refresh the page afterwards.

Also, it won't work on certain special pages, like Chrome's "New tab" page (or any other internal pages, like the "Downloads" page, "Settings" page, etc. It also won't work on any of the Chrome webstore pages, so it won't show if you try to resize the page while you're still on the extension's install page. This is a Chrome security feature and is true for all extensions; no extension is allowed to alter those pages.