The extension works in devtool environment, so it can read the resources' information. You will need to
restart your browser or re-open developer tool panel, and switch to the
Resource Saver tab.
ResourceSaver tab won't be available in devtool panel while your current tab is on url
https://chrome.google.com/*
Switch Version
It is not working in incognito mode. You need to restart devtool panel in order to switch version