Because the add-on no longer works since Firefox 32 (released on September 2) and the SSL certificate expires soon the service will be taken down on November 1, 2014.
Both the server and the add-on suffer from serious bitrot. Since Firefox 32 is released it is known that some users can not connect anymore.
Rewriting the original authors add-on and server in Node.js is somewhere on the back of my mind but I don't see it happen anytime soon, because of a lack of time. If you are interested in leading or helping with this effort please let me know.
You can manually add this proxy to your add-on settings using the following data:
Note: if you experience 413 or 400 Bad Request errors please use the customized GoogleSharing add-on.