Some attachments can't be viewed from your phone.
That's why I recommend using your desktop to complete the course.
If you get an error message about an attachment, please access the course through your desktop and you will be able to easily access everything. This phone app is awesome, but this is one limitation.
You know what, just to make it even more convenient, here's a Sparknotes style PDF that was made by one of the docs who took our course. He's packed up a bunch of references and some of his own notes from the course. Download it now and keep it handy. (Scroll to the bottom and click download link on the left titled "Implant Ninja Pocket Guide")