Installed the mass mailing app. Created a new address list. Edited the popup, made it Public.

On the website I added the popup to the front page. The popup comes up perfectly, but after I have added an email adress and clicked Subscribe.  Nothing happens  .. (The e-mail field grays out for a short while, but I don't even get the Toast and there's no email recorded in the backend. 

Is there another way of doing this ? Or is there some debug info I'm missing, because there nothing in the server log.