ArcGIS Server services URL '<https://server.domain.com/webadaptor>' cannot be validated against '<https://server.domain.com/webadaptor/rest/info>'

Error Message

When validating an ArcGIS Server federated with a portal authenticated with Integrated Windows Authentication used on ArcGIS Web Adaptor, the following error message is returned:

Error:
ArcGIS Server services URL '<https://server.domain.com/webadaptor>' cannot be validated against '<https://server.domain.com/webadaptor/rest/info>'

Cause

The authentication method for the web adaptor for the federated ArcGIS Server is set to the following:

• Windows Authentication is enabled
• Anonymous Authentication is disabled

Solution or Workaround

Change the authentication method settings for the web adaptor using Internet Information Services (IIS) Manager.

1. On the machine, navigate to Start > Control Panel > Administrative Tools, and click Internet Information Services Manager to open IIS Manager.
2. In the Connections window, navigate to Sites > Default Web Site > server, and click Authentication under IIS. 
3. Right-click Anonymous Authentication, set as Enable.
4. Right-click Windows Authentication, set as Disabled.

5. Validate ArcGIS Server using the ArcGIS REST API. Refer to ArcGIS REST API: Validate Server for more information.