If your entire course has a low accessibility score, you may want to reprocess it to ensure accurate reporting.  To do that, navigate to the panorama link in the navigation bar or add it to your navigation bar so you can access it.  

Once you select the Panorama choice, you will be prompted to navigate to the Panorama application.  on the left-hand side, you will see some options.  Make sure to select the Course Report selection.  This will allow you to see the accessibility score and other options for your course.

Now that you are on your course report, you should see at the top the option to reprocess the entire course. 

Please take not that depending on how much content is in your course this could take up to 24hr to reprocess.