Sometimes the camera gimbal doesn't rotate to the right angle (towards the ground), and keeps horizontal during the mission, it might be because of one of these reasons:
a. The ground at the takeoff point is not level.
b. Drone is powered on while holding it in hand.
c. Something is on the way or hits the gimbal while the drone is powered on and prevent it from stabilizing correctly.
And sometimes there isn't any specific clear reason.
The important thing is, that if it happens, you should see it when the drone sends you back the sample image.
If you see that the sample image is not in the correct angle, please do one of the following:
1. Land the drone, power it off and power it on again while making sure it's on a level surface.
2. While you see the sample image on the screen, push the left scroll wheel on the remote controller all the way to the left for about 7 seconds. This will turn the gimbal all the way down to the ground. After doing so, take a new sample image and if now it looks good, press the play button and start the mission.
In any case, don't start a mission (pressing the play button) if the sample image that you see on the screen is not set correctly or doesn't look good, because all the images in the flight will be like the sample image.