Tap on the music note icon on the bottom of the screen in the app and Sonos Radio should be one of your music service options.

Can you screen shot it. I don’t see a “music note” on the app

I see what you are saying, but it’s the same “Sonos Radio” I’ve always had...how do I know it’s HD

Can you skip and replay songs on Sonos radio stations? If you can, you have Sonos Radio HD.

I have got exactly the same problem trying to activate the HD service. On my Sonos account on the web I clicked on “Try it now” but brings me back to the same page mentioned by Brttlt. Maybe the HD service is not available outside of the US ? On the Sonos app on iPhone instead I do not even know where to go for activation. Please help, thanks.

It say to “reboot”. How do I reboot?

Depends on what you need to reboot, but generally speaking, you unplug a device from power for a couple of minutes, then plug it back in.