How to RE-migrate.  

This addon don't update. It only does a fresh migration. I'd recommend Uninstall (not just delete and if you don't have important data) wpForo and remove all tables then install a fresh wpForo and do a fresh migration.

Also don't foreget to remove _go2wpforo table from database before doing the second migration. But please don't delete it after migration, it used by Rdirect2wpForo plugin for URL 301 redirection.

Posted by: Robert

Also don't foreget to remove _go2wpforo table from database before doing the second migration. But please don't delete it after migration, it used by Rdirect2wpForo plugin for URL 301 redirection.

Does this imply its ok to delete all bbPress tables after migration?  (since this is used for the redirect) ???

Yes you can remove bbPress after making sure all data is migrated correctly.