Hello VictorDTG,
Thanks for asking the Apple Support Communities for help with Heavy Rotation on your Apple Watch.
This article talks about Heavy Rotation: Add music to Apple Watch - Apple Support
"Apple Music subscribers and non-subscribers can also choose to have Heavy Rotation added to their Apple Watch. Heavy Rotation is a collection of albums and playlists selected based on your iPhone listening habits."
If your iPhone is not nearby, please check this article: Use your Apple Watch without your iPhone nearby - Apple Support
If your iPhone is nearby and paired correctly, you might try turning the Heavy Rotation feature on, and restarting both devices:
iPhone User Guide: Restart iPhone - Apple Support
How to restart your Apple Watch - Apple Support
Then, turn the Heavy Rotation off again. If you still have issues, you may want to remove your music, and resync it to the Apple Watch. Add music to Apple Watch - Apple Support
Thanks and have a wonderful day.