All users in an ArcGIS Online organization cannot sign in to ArcGIS Image Dedicated

Description

When all users in an organization cannot log in to ArcGIS Image Dedicated, there may be an issue with the organization's security settings.

When collecting network traffic, there may be a message in the Console tab stating:

"Access to this application has been blocked. Please contact your administrator to allow access to this app."

Solution or Workaround

1. Try clearing the browser's cache, or trying multiple browsers and/or machines.
2. Confirm user type and role, and that they have access to ArcGIS Image Dedicated.
3. If the above points look fine, go to Organization > Settings > Security in ArcGIS Online, and turn on the Members can only sign in to external apps that are approved toggle. If it is enabled, try turning off the option to see if it resolves the issue.