Cloud with a cross on many songs

My iCloud Music Library contains many songs with a cloud and cross icon signifying the track has been removed using another device. But the only other device linked to the account is my iPhone and I haven't used that to remove any songs.

I store my iTunes library on an external hard disk and this was plugged into my Mac when I subscribed to Apple Music. It uploaded missing albums successfully but many albums that are in the iTunes library won't sync to my iCloud Music Library instead showing this icon.

Please help!