We have restored the missing files and the site is back to fully functional.

We have identified and resolved the issue for images and PDF files going forward. We currently working to restore the missing image and PDF files.

We are currently aware of this issue and working diligently to solve this.
If the PDFs are not opening properly within a lesson. The current workaround for this issue is to re load the page and this should resolve the issue for now. This is a temporary fix until a more permanent solution is found.