Are you standing on the scale barefooted, or wearing socks/shoes?
Is the scale showing your initials after you stand on it, or is it showing "???" instead?
It will only show the body composition metrics when it can get a reading through your bare feet, and when it identifies the person that's standing on it - if it can't do either of those things, then it will only display your weight without any body composition metrics.
Odd. And you're sure that you have the BF% "widget" turned on in the scale's settings? (I'm assuming you do, since you said it does show up at least sometimes).
I'm out of ideas. Maybe try pulling the batteries from it and putting them back in, and unpairing and re-pairing it with Connect. If those all fail, then contact Garmin about warranty replacement
