In order to change the order in which your lessons show, please follow these instructions.
Firstly make sure that no users have purchased access to the Certification Path. To do this, go to the Certification Path manager page, select the certification path that contains your lesson, then click the Clear User data button at the top of the page.
If somone has access to it, then you cannot change the order for database integrity reasons.
Step 1: See the Lesson order in the front end.
Step 2: Go to Course Manager and select Manage Lessons
Step 3: Change the lesson order by clicking on the arrows.
Step 4: See the new order in the front end after refresh.