There is no such thing as an "account" at Nabble. There are thousands of forums hosted by Nabble and you need to register at each one if the owner of the individual forum requires that before you may post.
If your forum has gone it is most likely that you missed an email from Nabble warning you it was due to be deleted because of a lack activity.
Check your spam folder for a message that says it has now been deleted and which will give you a link where you can obtain a zip file containing an archive of all posts.
Post that link in the Forum Recovery Request area of this forum.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.