Amazon Music recently stopped functioning on my Sonos One, although it works fine on Echo devices.
The first symptom was the following message: "Unable to browse".
I tried the usual, disabling/enabling the skill, restarting the router, etc. Then I tried to disable Amazon Music in services in the Controller, and re-enabling it.
When I get to the stage where I need to "Click Allow to sign in to Sonos", I click and end up on https://sonos-eu.amazon.com/
, where I get a page telling me "Website temporarily unavailable. Our website is currently unavailable whilst we make some improvements, etc."
I've looked around in the forums, and have seen no announcement regarding this, or no-one else having the same problem, at least not recently and definitely not today 1 Dec 2018.