If you are trying to access a published notebook link and you receive the message "Nothing found for that URL", it is because you do not have permissions to access the notebook.
Notebook security settings can be set so that only Aha! users can see them. Further, when notebooks are secured in that way, you must explicitly make each notebook visible to the team or teams you wish to have access. Teams are defined by the product and/or product lines to which they belong.
To first confirm that you have enabled notebook security in this manner, go to Settings -> Account -> Security and single sign-on. Look for Enhanced notebook security settings and verify that Only Aha! users can access web notebooks is selected.
To grant explicit access to users for viewing notebooks, go the Notebooks menu and click the gear icon to go to your settings.
Toward the bottom of the Notebooks settings, you'll see the section Visible to Product teams:
Check the products and/or product lines for the teams who should be able to view the notebook.
Note that you should also verify that the user trying to access the notebook has permissions for the product teams that are selected here. You can do that under Settings -> Account -> Users.