The same scenario happens with all three of the Music Services that I've attempted to add (Amazon Music & Audible & Sound Cloud.
I go to "Add Music Services", then select a service. I then click the button that says "Add to Sonos". I then click the button that says "I already have an account". And then on the next screen there is the "Authorize" button. You click this button and nothing happens for approx. 5 minutes and then a screen appears that says to check my internet connection and come here.
I've noticed that there are plenty of other people that have posted this question and one solution is to update the sonos controller on a Windows 10 platform. I don't have one of those and I never saw any other solutions so please help