This is normally caused by an issue with your current session. To fix this please do the following:

On PC:

Click the 'Logout' link in the top right of the screen. This will take you back to the eBooks.com homepage.
Click on the 'Sign In' link at the top of the page and log back in to the website.
Once you are logged back in to your account try the link again.

On mobile:

Tap the menu icon in the top left, then tap the 'Logout' link at the bottom of the menu. This will take you back to the eBooks.com homepage.
Tap the menu icon again and tap 'Sign In' and log back in to the website.
Once you are logged back in to your account try the link again.

If this does not work please complete our support form to submit a ticket to our customer support. Please send the URL of the page you are on and if possible a screenshot of the page. Let us know which link is not responding. We can then investigate.