MP3s not playing on Apple Watch Series 3; songs are greyed out and won’t start

I tried adding some mp3s to my Apple Watch Series 3 and it’s mostly worked but songs are greyed out and when I press them nothing happens. I can open a album and playlist but it will not play any song and when I press the play button it goes straight to not playing

[Re-Titled by Moderator]

Original Title: mp3s on Apple Watch not working