First, make sure that your Divi Poppyz theme is updated to at least version 1.3. Update it from here.

This will disable all comments by default if Divi Builder is being used by a Course or Lesson.

To enable comments on a particular lesson or course using Divi Builder:

  1. Add a Comments module in a section where you want it to appear.
  2. Scroll down to the bottom and make sure Allow Comments is checked:

    This is checked by default unless Comments are disabled in WordPress Settings. Disabling comments on WordPress will result on future posts’ Allow Comments to be unchecked. To do this go to Settings -> Discussion

    Note: If you can’t see the Allow Comments section  below the course or lesson, you may have to display it by clicking on the Screen Options button on the top right of the screen, and checking Discussion:

If both of these are followed then the Comments section should appear. Note that this must be done on each course and lesson.