I think it is your theme, but of you are only having one forum, then you could create a page called anything and put
[bbp-single-forum id=$forum_id] – Display a single forums topics. eg. [bbp-single-forum id=32]
you can find the ID of your forum by looking at the number in the url when esiting it ie in
dashboard>forums>all forums>edit forum
and use this page as your forum page.
It may work, it may not 🙂