ARC doesn't work using CarPlay

I have the latest software on the iPhone, Mac which runs Roon, Roon on Mac and iPhone, 5G on iPhone, 1.2Gb internet speed into home. ARC comes up with the initial screen but get the error poor connection or internal playback error. I can use Tidal in the car on CarPlay with no issues. When I test ARC in the Roon app on the Mac, it comes back as Ready. What should I look at to get this fixed?

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