[Plugin: Mailpress] Stopped working

Hi,

I’m using Mailpress on a site for several years now, without any problems. Until this week. Without any reason it stopped working. When I send a test-mail it works fine. But when I publish a post with in the newslettercategory nothing happens. The post is visible on the site, but it isn’t listed in the send mails.

Anyone a suggestion?

Erwin