Please let me know either the email or username for your account (do NOT give password), as well as the specific books this concerns. Please also check your spam or junk folder in your email program to make sure responses from booksonboard.com aren't being unintentionally redirected there.
The distributor for book 4 has been exchanged so that should work now. We're not detecting any errors with 7 or 8 however. What specific error message are you getting? And what are you attempting to download to?