Why some music files aren't playing via Bluetooth in car?

[jeobsplyr]

I have a 2016 Hyundai Elantra w/ Bluetooth Audio. I use an LG G3 with some MP3 files stored on an SD card. My problem, the files that were on the phone when I got the car plays fine. Every music file I've put on the phone since will not play. When scrolling through the list of songs, newer files don't appear. I tried unpairing, then pairing the phone with the audio system without any luck. Am I doing something wrong???