When you encounter an unexpected issue (for example, missing courses, exercises, lessons, or elements on a page), this is often because the cached content in your browser has not updated properly. To refresh your content, try this generic troubleshooting technique:
Log out from all Academy/Community/Pega.com related sessions.
You mentioned Chrome and IE. Did you mean it only failed in those browsers, or that you tested in both so it seemed browser agnostic.
If the latter, then perhaps the service was down temporarily. If the former, I would like to know more.