Some purchased music plays only on Mac, not on iPad nor iPhone

Hello! I own music that is available and will play on my Mac, but not on my iPhone or iPad. The titles show up on the iOS devices, but are grayed out. There is an icon of a cloud next to the play time for each of these titles. If I attempt to play one of these, I receive a message that the “song is not synced across [my] devices”. It instructs me to select Sync Library in Apple Music on my Mac. However, Sync Library is already selected. Any advice, please?