It seems that your blog cannot contact the license validator. Ask your provider to unlock the HTTP/HTTPS connections to http://www.thenewsletterplugin.com
http_request_failed – cURL error 28: connect() timed out!
As reported in the error: “Ask your provider to unlock the HTTP/HTTPS connections to https://www.thenewsletterplugin.com”. Your blog is firewalled, cannot connect to the license validator.