It has to recognize you from your background for this to work, if the Front LED's are red or blinking red it hasn't recognized you and you need to put your arms in the air in a Y shape for about 2 seconds or until they turn solid green, then it will start to track you. If you can't get it to recognize you be aware of the light, where it's shining, where shadows are, etc... Best results if you stare directly into the sun, arms up, until it recognizes you there, then you can do whatever with it. I had this problem my first flight but soon fixed it by positioning it so I would look at it and would have the sun in my face. It struggles A LOT when you turn your face and body into a shadowed position, so try to keep it in the light when using gesture controls, or fly when/where the sun is not directly on you, but still bright.
Mind you, I think the drone is sexist...

I was showing my girlfriend how to use all the controls and it recognized her hand and followed it Anywhere... Stick my hand up, nothing. It recognized it! But the second I tried to move it the thing would stand like a rock... Maybe budging an inch or two before giving up on me

Eventually I just let her position it for photos xD