hey sorry to know that it wasn't working when you tried it. Actually I haven't updated from some time because whatsapp was continuously changing and updating from few weeks (beta and multidevice feature) and since it (extension) heavily depends on its (whatsapp web) architecture, it breaks down. I am gonna soon release a update if I found changes aren't happening anymore on the whatsapp web. Thanks for staying tuned.
Edit :- It's working now!