This may mean that you are not being recognized as a site license customer for a given journal or article. Please make sure that your administrative account is up-to-date with your current subscriptions and correct IP address(es).
To view your administrative account, please go to www.nature.com/libraries.
Enter your administrative username and password. If you do not know it, then please contact Customer Service.
Also, make sure that the article you are trying to access is covered by your subscriptions; for example, in order to access an article in Nature prior to 1997, your institution needs a separate site license to the Nature Archive.
If your subscriptions are current and your IP addresses are correct, but you are still being denied access to your subscribed titles, you can submit a query to our Online Service team via our webform here. If you would rather email or phone them, their contact information is available here.