You should check the hight of the waypoints compared to the current hight. What I could think of is that it didn't do a good "Geo init" and doesn't have the correct height.
The other thing I could think of is that if you have a joystick connected you should set it into NAV(AUTO2) mode, and give no thrust at the Start engine block(else it can't start the propellors) and give full thrust after the propellors are turning before entering the Takeoff block.
1. The Geo init block: This one updates the waypoints positions and height of the drone in respect to the current GPS position.
2. The Start engine block: This block starts the propellors at the lowest speed, so they should be turning but it should not take off.
3. The Takeoff block: This block let the drone takeoff and go to the next block in the flight plan. So then it should really go to STANBY for example. (Keep in mind that if you have a joystick connected you must give full thrust, because the thrust of your joystick is the limit of thrust the drone can give)