McIntosh MB 50: stream from iTunes on Mac?


I just set up the MB50 and can stream music from my iPhone (Music app) and my Spotify account but the main source I want to access is my iTunes on my Mac Pro 6.1 running Mojave.  I choose Media Server as the source on Play Fi but it can't locate any server.  Home sharing is turned on (logged off and back on) on the Mac.  The iPhone, Mac and MB50 are on the same wifi network. 

What is the procedure in getting Play Fi to access iTunes?
ymc226