By default Nabble allows anyone to post a new topic, so by itself that does not prove you are logged in.
Please confirm that you are logged in (I.e. can see your username towards the top right of the forum, and not the Login and Register links.)
If you are logged in it will help Nabble trace the problem if you post the URL of your forum and confirm what browser you are using.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.