Are you using the standard sidebar or Widget Framework (which you have been posting in recently)?
If the standard sidebar then you need to enable the profile posts in the sidebar block
ACP > Options > Node & Forum List
Set "New Profile Posts Display on Forum List" to 5 (or any number other than 0 which disables it)
If you are using Widget Framework, then you need to add the New Profile Posts widget and ensure that it has the position set to forum_list. If you have caching enabled in the widget, you will have to wait for the cache to refresh, alternatively set it to 0 to disable the cache.
For any further questions relating to this and Widget Framework, you should post in the discussion thread for that add-on.