The link for the login page to Scientific American has changed. The new link is the following:
https://www.scientificamerican.com/account/login/
instead of what's in the recipe:
https://www.scientificamerican.com/my-account/login/
this link redirects to the Scientific American home page.
Attached is an updated recipe that works well.
Edit: for some reason that is beyond my level of expertise, using a username and password in the builtin recipe leads to this error: mechanize._response.get_seek_wrapper_class.<locals >.httperror_seek_wrapper: HTTP Error 404: Not Found
Edit: this does not happen when the recipe is opened and edited using the "add or edit a custom news source" option and the username and password are manually entered into the br["emailAddress"] = self.username (replacing "emailAddress" with the username/email address and the line below "password" with the password, and then downloading in the edit custom recipe window ("Download this recipe").
Edit: Also the built-in recipe downloads just fine without a password or username.