Hi.  Are you saying that when you press “Add Content Service” in the app, it doesn’t offer you Amazon Music as an option?  If so, check that your location is correct in your online Sonos account.

If you have not added it because you haven’t found the place in the app to do it, then go to your account in the Sonos app and select “Content Services”, then “Add Content Service”.

if the above does not help
 

With the Sonos online account address, even if it looks correct delete it and add again.
 

Also check your Time Zone / date & time are correct in the Sonos App, then again in the Sonos App use the check for updates as this also forces the Services list to update.

Moderator edit: added quote prior to marking Best Answer

Thanks, I went in last night to my online profile and added my address (as the system was setup in my basement by an AV company).  I just changed the time zone in the app now as that was also not set.  I did a refresh and no change yet so hoping these settings are just getting updated in the system. I will check again in a day as I am hoping this fixed the problem. 

I’m facing the same issue. 
 

just got an era 300 and want to stream from amazon music but it isn’t an option to add it as a service. 
 

I’ve also updated my address and time zone, but no luck yet. 
 

Have you managed to find a workaround @Banksy17 ?

Have you checked for updates to make sure your Sonos  system and controllers are fully up to date?

I believe I have done the updates. I installed them the day I opened the boxes. 
 

still no luck yet unfortunately. 

I’ve tried all of the above and everything BUT Amazon Music appears as an option to add in the “Add Content Services”.