bbPress.org

I think you are using the 2023 theme.
This is one of the new FSE themes, so you need a fix to work with bbpress.
install

bbp style pack

once activated, navigate to

dashboard>settings>bbp style pack, and you should see the first tab called ‘Theme Support’ – if you don’t see this, come back.

In that tab, select

Enable Theme Support

and save

The forums should then display