Welcome to Apple Support Communities.
We understand that you have removed the explicit lyrics restrictions on Apple Music for your children. We are happy to assist.
Do you know if Apple Music has been signed out of with their Apple ID. If so, you will lose any downloaded content. Are any other playlists missing? Did you recently turn on Sync Library. If so, please try the steps here as they may help: Use Sync Library to access your music library across your devices - Apple Support
"How to turn on Sync Library on your iPhone or iPad
- Make sure that your iPhone or iPad is signed in with the same Apple ID that you use with your Apple Music subscription.
- Go to Settings.
- Tap Music.
- Turn on Sync Library.
- Turn on Sync Library on your other devices."
Let us know if you have further questions.
Take care.