What does 401 Unauthorized mean

The '401 Unauthorized' error message happens when the server is looking for an encryption key from your computer (the client's computer), and it can't find it.

Chances are you didn't enter certain setting correctly. Double-check that your settings are correct or that your username and or password is entered correctly.

Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided.[2] The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource.
source en.wikipedia.org