Perhaps the editor is looking for some tragedy behind the sunshine. Usually, soulful beautiful love songs begin from pain rather than just as an ode to the perfect romance. Completely blind to the circumstances, is there perhaps someway you make the artist's rise to where he/she is today a bit more dramatic? Not the the point of embellishment, but try to isolate some adversity.
Just a guess because I read a lot of profiles of musicians and there does seem to be a common outline to the musician's story. Perhaps find a way to better fit this person's actual story into that mold while remaining true to the piece.
I actually was able to interview Matchbox 20 as a kid, about 2 weeks before "Push" became a huge hit. The editor I was writing for was upset at the piece because it seemed like it was for a kid's magazine (I was about 15 at the time and hiding my age from the editor, but the band answered my questions in a very "Nickelodeon" way). So, I made it more gritty with some of their worse gigs, stories told humorously but I slanted them less so to please the editor's sense of drama.
Hope it works out.