The pages do not match! Timestamps differ or were not found!
Things you can do:
Load your homepage in a logged out browser, check the timestamp at the end of the html source. Load the page again and compare the timestamp. Caching is working if the timestamps match.
Enable logging on the Debug page here. That should help you track down the problem.
You should check Page 1 and Page 2 above for errors. Your local server configuration may not allow your website to access itself.
Hi and welcome to the forum! WP Super Cache’s tester might not work due to this security system:
So I think you should follow the things you can do that are available in the error you were given (especially the first one) to see if the uncached page’s and the cached page’s timestamps match on your website.