The Apache "401 Unauthorized" response may return when attempting to access a page where HTTP Authentication is required. While the response is similar to an Apache "403 Response" where access must be allowed, the error comes explicitly from a lack of credentials to a page.
When the error returns from a cPanel Server, a common response received within your browser will look similar to:
[user@server ~]$ curl -IL https://www.domain.tld/
HTTP/1.1 401 Unauthorized
Date: Thu, 1 Jan 1970 00:00:00 UTC
Server: Apache
AuthName "Restricted"
AuthType Basic
AuthBasicProvider file
AuthUserFile /home/user/.htpasswd
require valid-user
</FilesMatch>
These entries are added within the cPanel >> Files >> Directory Privacy interface. The credentials cannot be viewed from this interface. If the credentials for a page are lost, they would need to be recreated from this interface.