It's possible the "system" (computer/tablet/mobile device) has problems opening and running "Adobe Air" (.air) files, which is the format the Book Of Shadows is in.
We've created a special page where people having problems installing can download every component of the course, including the Book Of Shadows in a "friendly" format that should work on all devices.
Please click any support link on this page to open a support ticket and include your order number or email address, along with a request for the mobile-friendly download page, and we will send it over to you.