You need to break it down as much as possible. Is the traffic you are getting going into the front page? Are they going to any other pages on your site? Have you created some starter discussions for them to read through? Do you have a call to action on your site asking people to sign up as members? Are people clicking into the sign-up page but not signing up?
try to participate in social networking sites, and gain friends there that has interest in your niche, try to encourage them to join your forums as well, and also give them a good reason why to join your forums, also optimize your website to gain traffic.
IMO, you need to participate in other forums to let those members know about your forum. Also, you should join the social bookmarking and networking sites to get visitors for your forums. And, as everybody knows that content is a king, so put some interesting content and threads on forum so that visitors will get attract to it. As well as banner advertising and link exchange is the best way to get traffic to the forums.
Same with me guys... I have the same problem with my forum...But I also have a main site with 2000 uniques a day but still can't get the conversation flowing at the forum. I know there is alot of competition for this nieche but I know it will be ok soon.. http://www.pctipforum.com
I am also having the same problem. Im getting unique traffic, but no sign ups or maybe one every other day. I know there are a lot of other places you can go to talk about working from home but the forum is geared toward an ebook we have. Any suggestions for whatelse i can do? I put up unique content alot to encourage more movement but still waiting to see whats going on