Music playlist will not sync to iPhone

Several music playlists will not sync between my iMac and my iPhone.  They have synched with my iPad so only my iPhone is the problem.  I subscribe to Apple Music and I have followed all of the steps in the below article:

https://support.apple.com/en-us/HT204926

iMac is running macOS Big Sur, Version 11.2.1.  iPhone is model 12 with IOS 14.4. Any assistance would be greatly appreciated.