Unable to access the ArcGIS Enterprise portal configured with Integrated Windows Authentication or Single Sign-On

Description

In some instances, when an organizational user attempts to log in to an ArcGIS Enterprise portal site configured with either an Integrated Windows Authentication (IWA) or Single Sign-On (SSO), the login fails and the user is unable to access the portal site. The following error message is returned:

Error:
Invalid username or password.

Cause

The user's machine Internet options settings page is not set to automatic logon for User Authentication.

Solution or Workaround

Note: 
The following workaround may require the assistance of a system administrator. Consult a qualified computer systems professional if necessary.

1. On the user's machine, navigate to Control Panel.
2. Click Network and Internet.
3. Click Internet Options.
4. In the Internet Properties window, on the Security tab, click Local intranet.
5. Click Custom level....

6. Under Settings, scroll to User Authentication, select Automatic logon only in Intranet zone, and click OK.

7. Restart the machine, and log in again to the ArcGIS Enterprise portal.