You may encounter pages where AdBlock doesn't work the way you expect it to. When you click the AdBlock button in the browser toolbar, most of the items that normally appear in the AdBlock menu are not there. The AdBlock button also turns gray in some browsers, indicating AdBlock is not fully functional.
This happens because "internal" pages in all browsers, including Chrome, Firefox, and Microsoft Edge, are not accessible to extensions. Internal pages include the New Tab page, the extensions manager, the browser's settings, and so on. Browsers don't allow extensions to inject code into these pages because these pages can change the way the browser behaves. Allowing extensions to possibly co-opt the browser would be a security risk.