How to sync iPod nano 7th generation to Mac Tahoe

I have two iPod Nanos, both 7th generation. In the past I have had no problems sync-ing them to my music library. I have gotten a new 24" Mac (running Tahoe) and now neither of them will sync. I get a "Loading" message, but nothing seems to happen. I tried restoring one of them to factory settings, and that would never complete. Now that Nano is completely useless. I there anything I can do it get it working again? And how do I get the other one to sync?