Hello Blueskiestoday,
Thank you for using Apple Support Communities. Sounds like you're missing songs after turning on Sync Library. If that's the case, we'd like to share a helpful resource that has steps you can try: If songs are missing from your music library after you turn on Sync Library - Apple Support
Perhaps you can even update your Cloud Library by following these steps here:
Search for the missing song on your computer
1. Search your Mac or PC for the missing song.
2. If you find the missing song, drag the song to the Apple Music app or iTunes.
3. In the Apple Music app or iTunes, choose File > Library > Update Cloud Library.
You can even try to toggle off Sync Library and turn it back on to see if that helps with your missing music.
If your issues continue to occur, try installing any pending updates you might have available on your Mac. This step can help isolate possible software related issues: Update macOS on Mac - Apple Support
We hope these steps do help you. Thank you for using Apple Support Communities.