Unable to add portal connection in ArcGIS Administrator

Description

In ArcMap, portal connections are made to share projects and access content from members from an organization in ArcGIS Online or Portal for ArcGIS. A portal connection can be made using the Manage Portal Connections tool in ArcGIS Administrator. However, attempting to add a portal connection in ArcGIS Administrator fails, with the following warning message returned:

Warning: 
The URL specified does not appear to have a running Portal for ArcGIS.

Cause

• The URL containing portal components cannot be reached by ArcGIS Administrator as the URLs are not allow-listed.
• The credentials from a user's input do not match the credentials in Credential Manager. This usually happens when upgrading to a new version of Portal for ArcGIS or if the password is changed.
• The user does not have permissions to the registry keys used to store the portal's information.

Solution or Workaround

Depending on the cause, follow these steps:

Allow-list the URL containing portal components

Note:
Contact the organization's IT department to carry out the following workflow.

Allow-list the following URLs:

• Portal for ArcGIS

http://<webadaptorhost>.<domain>.com/<webadaptorname>/home

https://<webadaptorhost>.<domain>.com/<webadaptorname>/home

• ArcGIS Online

https://www.arcgis.com/home

https://<organization>.maps.arcgis.com/home

Update the portal's password in Credential Manager

1. On the portal machine, navigate to Control Panel > User accounts > Credential Manager.
2. Update the portal's password in the Portal entry.

Give permission to the user to the machine's registry settings

1. Navigate to the Windows Start menu. In the search bar, type regedit and press Enter. If prompted, click Yes in the User Account Control window.
2. In the Registry Editor window, navigate to the following folder path:

Computer\HKEY_CURRENT_USER

3. Right-click ESRI, and click Permissions.
4. Under Group or usernames, select the user that requires permission to the registry folder.
5. Check the Full Control and Read checkboxes.
6. Click Apply, and click OK.