There are already several discussions here:

https://en.community.sonos.com/amazon-alexa-and-sonos-229102

Seems to be incredibly widespread (perhaps a Sonos server issue?) and I can only hope they post something about being aware and working on a fix once work hours begin ion the West coast.  

My Beam and One still isn't working with Alexa. I can add speakers within the Alexa app, and they appear in the Alexa app, online but uncontrollable by voice. When trying to add the Alexa voice assistant in the Sonos app it creates duplicate offline speakers in the Alexa app, which can't be controlled, and the voice assistant doesn't appear to have been added in the Sonos app. All worked couple weeks ago, and stopped on 14th. Have tried absolutely everything, disabling and enabling the sonos skill, resetting the router, checking the IP addresses in the router, trying with a different phone device etc etc. There are obviously some settings somewhere causing my issue. I've had enough! Only had them couple of weeks so they are going back to the shop and I'll get another brand.