It is a good Add-on, but I found it did not work for a long time. Lucky, I solved this problem today, after updating to the new version of Firefox.

When I try it today again, a pop-up message is come up. it tells me to change the setting of cookie to make it function.

Pls try:
1. go to Firefox "Setup"
2. find "Cookie" setting
3. find "接受來自第三方的 Cookie" (English may be: Accept 3rd party Cookie (sth likes that)
4. choose: "造訪過的網站" (English may be: website visited (sth likes that)
5. close the setup page

It should work now. I tried. hope you can solve it as well.