The Sign In option is not available on the ArcGIS Enterprise portal

Description

In some instances, when attempting to log in to Portal for ArcGIS configured with Integrated Windows Authentication (IWA), the Sign In option is not available on the portal's home page, as shown in the image below.

Cause

The user account is not a member of the portal.

Solution or Workaround

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

When using IWA, logins are managed through Microsoft Windows Active Directory. To resolve the issue, add the user account as a member of the portal, followed by enabling anonymous authentication on the ArcGIS Server site.

1. Add the account from the related identity provider as a member of the organization's portal. Refer to Portal for ArcGIS: Add accounts using the portal for steps to do so.
2. On the ArcGIS Server site, disable IWA to allow the site to read the portal's users and roles from IWA. Refer to Portal for ArcGIS: Configure your portal to use IWA for more information.
3. On the ArcGIS Enterprise portal's home page, click the Sign In option, and log in to the portal using the provided credentials.