Check for errors in the URL. It's possible that the 401 Unauthorized error appeared because the URL was typed incorrectly or the link that was selected points to the wrong URL—one that is for authorized users only.
If you're sure the URL is valid, visit the website's main page and look for a link that says Login or Secure Access. Enter your credentials here and then try the page again.
If you don't have credentials or have forgotten yours, follow the instructions provided on the website for setting up an account or resetting your password.
Regards,
J Wick