This is a persistent issue for some weeks now. Since recent changes to att.com I can login to my account online but then the message appears "Please give us a moment. We're almost there!" and the blue circle just keeps spinning and goes nowhere. The browser is Firefox 53.03 64 bit and the OS in Linux Fedora 25. Chrome works with the site but not Firefox and this is only since recent changes ATT have made to their site. The response I received from ATT tech support was downright dismissive
“Oh if it works with Chrome but not with the other browsers then we are not going to fix that” - or words close to that effect. Not the kind of response you would expect from a professional service. The technical support person also said that they new that Safari had issues with the new site, too. Firefox and Safari are major browsers. If ATT's web developers are not competent or too lazy to develop for all the main browsers then perhaps they should find employment elsewhere.