My guess is that your baklinks are forum profile backlinks, and not backlinks posted in forum threads. Because of that, none of them have been seen by google. You have to ping your links as well because google havent crawled the forum links. There are also backlink indexing services like backlinkbear, lindexed, backlinksindexed. These services will make your backlinks visible. Maybe some links are going to be visible in time if googlebot crawls them.
Some link building services also make "link pyramids" where they give backlinks to your forum backlinks. When mass linking to their own backlinks, people often use software like BMD, Xrumer or SenukeX, but those might not be good to use directly on your own site, because google in worst case could deindex your site.
Some services make microsites with aged domains and give backlinks to the forum links, and also backlinks to the microsites.
