If you receive the following error, "Currently this single sign-in feature is disabled for the domain mycompany.com" you will need to enable OpenID for your Google Apps domain.
1. Log into your Google Apps account as an administrator.
2. Inside your Google Apps Domain, click Manage this domain
3. Click "Advanced Tools"
4. Under "Authentication" click "Federated Login using OpenID"
5. Check the box labeled, "Allow users to sign in to third party websites using OpenID"
6. Save your changes then try again to launch ONE UP.