I uninstalled the extension, and then reinstalled it. This does not work:
From your screenshot I can tell that you're using an old version of the extension. I've changed the icons in the latest release (v.1.8.0) and the one you're seeing is an old one. The popup should look something like this:
After you get the latest version, please make sure when trying to resize a window that the current tab contains a page loaded using one of the following protocols: http://, https:// or file://. When resizing the viewport, the extension will fail if the active window is a Chrome "special" page, like the "Settings", "Extensions", "Downloads" pages or anything similar.
Also, please note that the tooltip at the bottom right side of the page won't be displayed on pages like the ones mentioned above, or any of the Chrome's Webstore pages (this is a Chrome security "feature").
One other thing worth mentioning:
In order for the extension to work on local HTML files, you need to open chrome://extensions/ in a new tab and enable the "Allow access to file URLs" checkbox next to the Window Resizer extension.
Thanks! I exported my settings, then reinstalled, then imported again. It worked!
Customer support service by UserEcho