When I click the link to your forum it goes to a "Forum no Longer Available" page. That would suggest it's been deleted.
Often that happens because of inactivity - but you should have received warning emails and even one sending you a link to an archive, so it could be restored in the future. Do check your Spam folder to see if such messages are there.
However, if the forum is deleted I wouldn't expect you to get a notice giving its URL.
It is also very confusing that over the last few months some of Nabble's system messages display under a "Jmeter" forum - but that part has become expected.
This does look like a Nabble issue that needs to be resolved - but do check if you have messages in your spam folder.
Just a Volunteer Nabble Helper - because the nice folk at Nabble have helped me! GregHelp - Building a set of answers to Nabble FAQs.