Airplay streaming to Sonos One from a Mac
I have a MacBook mid 2011 with macOS 10.13.6 and a Sonos One connected on the same wifi network as the MacBook. The Sonos does not show up as an output option either in the Airplay menu or in iTunes. The Sonos software has been updated with Airplay 2 support and it does work fine with my iPhone. Any ideas why no go from the Mac? Thanks.
MacBook Pro, macOS High Sierra (10.13.6), 15 inch, late 2011