Why does the first song play on my playlist and then the rest of the songs don't play?
Why don't the rest of the songs on my playlist play after the first one plays. It used to work fine.
As a first test...
Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?
Safe mode attempts to repair Disks & clears lots of caches, so if Safe Mode works try again in regular boot.