I am trying to say troubleshoot an issue if it could be something else like a theme causing the issue, so switching to a default theme could test that.
https://codex.bbpress.org/getting-started/troubleshooting/
Remember reply pagination does not show up if you have threaded replies enabled.
Here is a ticket to fix reply pagination in threaded replies, but for now the patch only works for forums that are not hidden or private.