If I remember correctly, "After the Deadline" uses an external service
to handle the "grammar information" for the language you are using. I
wonder if this error is telling you that the online portion of the
system is not working. Also, I believe that this grammar system was
still in "beta", the last time I looked at it in the Extension Center.
Maybe if you go online and do some configuring, you might get it to
work. At least you can contact the creators and find out what the error
actually means.
{quote}
After the Deadline relies on large language models to check your
writing. Because of this, it must communicate with a software
service. A default SSL-enabled server, hosted by Automattic, is
configured for you. The exact software and models hosted by
Automattic are available under the GPL from
http://open.afterthedeadline.com. It's easy to configure the
software service end point of your choosing from this extension's
options dialog.
{unquote}