Adding a Google Analytics ID to an ArcGIS Open Data 2.x site causes the following error when saving the site, "The subdomain you selected was used by another member of your organization before you were able to save this site. Please choose another subdomain."
Temporarily change the site URL, apply the Google Analytics ID, and save the site. Then, change the site URL back to the original, and save again.The video in the following link demonstrates the workaround steps:<a href="https://www.screencast.com/t/qZQOuQOu" target="_blank">https://www.screencast.com/t/qZQOuQOu</a>.