If you see the error message Authentication failed, you are probably trying to log into the University of London Portal. You can only log into this using a Portal username and password, and not an Athens account.
To access Online Library resources, search Summon and click on an item in the search results. You will then normally be asked how you want to sign in. Alternatively, login from your programme gateway.
For more information, see our I can't find where to login with my Athens account FAQ.