I think you need to find a more compelling way to help promote forums. I don't see any ads on the forum except for the buttons on the right that frankly, aren't in a compelling place, nor do they entice me to click on the ads.
If you can have ads above and below the forums, in the topic view, etc, that would be a good way to start. You have powerful software, you should be able to find a good way to incorporate your means of promotion that truly help your clients.