Problem Definition

As described at Troubleshooting Atlassian account, some users see the login button spinning and are unable to login to Atlassian Cloud where their browser blocks cross-site cookies.

The problem is there's no way to nudge these users to change the setting.

Suggested Solution

Detect if a third-party cookie is blocked on the client side (refer to stackoverflow.com), and show the friendly notice to enable third-party cookies.