AD SSO live users are regularly loosing the authentication of its live users.
First ensure you have integrated and configured active directory set up correctly. You can use the following article for the same:
If configuration is correct and still facing the issue, disable “HTTP challenge redirect on intranet zone” under services tab under authentication as shown below
HTTP challenge redirect on Intranet Zone
To secure and to prevent the user credential from going out on the Internet, device will redirect NTLM authentication challenge on Intranet Zone. Client will be transparently authenticated through device’s Local Interface IP and credentials will be exchanged in Intranet zone only.
This option will be useful but some time it could create an issue. So disabling this option might solve the issue.
Hope this article helps you.