HELP!: "Some of the files were not copied..."

I know many people are having this same problem;

mine is ever since joining Apple Music & updating iTunes, whenever I try to add files I have converted from youtube, like I have a million times, to my Phone 6, I get this message:

"Some of the files were not copied to the iPhone “Matthew's iPhone” because iCloud Music Library is enabled on this iPhone."

HELP!

Thank you. 🙂