Accessibility Help Needed!

Hi. I've just published a new course and have received the following feedback from the accessibility team for my organization: 

"I would say that the module is not accessible for users of screen reader technology. The software could not identify links, headings or other landmarks on the various pages. Users of screen reader software typically navigate around pages using the Down Arrow or the Tab key. Neither of these keys could move the "focus" of the software to elements of the pages such as the Next or Previous buttons, nor to the audio controls (which FYI also did not work even using the mouse). The software also could not recognize any links on the pages and could not read any text, such as in the various screens, pop-ups, FAQ and quizzes."

I've read through the articles and discussion threads on here but I don't know where to begin to address these issues. This is a big topic for our organization so I want to design smart from the beginning. Any assistance is gratefully accepted!