Lots of posts about this. It was also not working for me so I did some digging.
Its not a popup. Its a java applet from google used for analytics and tracking. Most security and privacy tools will block this for good reason. if this URL is blocked, Live chat will not work (and several other undesirable functions)
www.googletagmanager.com
I suggest cleaning up your site. It will remain on my blocked list.
Security and privacy DOES matter.
