iTunes 12.2.1.16 for Mac won't play iCloud Library, nor iTunes Library songs! (Apple Music works though-?)

iTunes 12.2.1.16 for Mac won't play iCloud Library, nor iTunes Library songs! However, Apple Music plays.

To further confuse me, when I play the iCloud libraries on my iMac that is Home shared from my Apple TV, the playback works fine.

If I attempt to play a song on the source player, it stalls out at less than a second into the timeline.

I've reviewed restarting, reinstalling, and unmounting and remounting external drive.

I have a Macbook with iTunes 12.2.0.145 on it and playback works just fine.

Is this something that will be fixed? Any suggestions?

iMac (21.5-inch, Late 2009)

3.06 GHz Intel Core 2 Duo

4 GB 1067 MHz DDR3

Using Glyph 2T External Drive to store iTunes Library (1.22 TB Free)