NEXT Button not working

When Next button becomes enabled, but nothing happens after you click the button, the first thing to check is to make sure you are publishing the whole project and not just one of the scenes. If you have only published the first scene, the Next button cannot jump to the next scene because it doesn't exist in the published course, but there is no error message detectable to end user.

Another thing that can make this tricky is that the setting for whether you are publishing the whole course or just a scene is preserved individually by Publish target, so it may be set to Entire Project for Review 360, but sets itself back to single scene when you switch from there to publishing for LMS if that is how it was last set for LMS.

Be careful not to miss that. Otherwise, you can spend a lot of time looking in your code for what is wrong with the next button trigger, when there is nothing wrong there.