I'm having issues as well.
Setup extension with RESTful api, using updated api url, running updated versions of mwz (1.3.8) and the extension (1.2)
Leads being added, nothing appears to be happening from bulkemailchecker.
http://imgur.com/a/DrqbZ
http://imgur.com/a/YpFKd
http://imgur.com/a/sa12I