This error message means that either no materials have been setup yet, or the mapping of the LMS course to the setup materials has not yet completed.
After seeing this message, exit the course, and then try again after at least 5 to 10 minutes. The mapping should have completed and should now display the materials.
If you continue to receive the error message, it could be that you have merged courses in your LMS. Please notify your bookstore manager if you merged courses/sections in the LMS.
If you continue to receive the error message and did not merge courses or sections in the LMS, then the material may not have been setup yet - check with your bookstore manager on the status. They can provide the setup status or escalate the issue for you.