Unit navigation bar missing next and previous buttom

Currently I’m using Bitnami for our Open EdX learning website. it’s akademy.akabot.com

When I create the course and open courseware, the unit navigation bar does not have the next and previous buttons.

I can’t move the to the next unit or next section but have to return to the course outline page. There is no navigation bar at the bottom of the unit either.

Is this expected behavior or we need to enable the features first?

I can’t see the next and previous button when accessing the course unit in EdX Studio too.

It’s driving me crazy.

Thank you.