my own music won't download from my Mac to my iPhone

Perhaps I misunderstood your reference to Apple Music to mean you had a subscription to the service when you were referring to your purchases for the iTunes Store. You might need to revisit your sync selections. See Sync your iPhone, iPad, or iPod using your computer - Apple Support.

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If you have a subscription to Apple Music then you typically wouldn't sync to transfer music as it should happen automatically through the cloud. DRM protected Apple Music cannot be synced over USB. See Turn on Sync Library with Apple Music - Apple Support. Is your computer authorized for your Apple ID. See also Identify cloud status icons in your music library on your Mac or PC - Apple Support. Perhaps the cloud status column will give some insight.

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