You mean that the gimbal control wheel on the remote doesn't work?
When you power up the aircraft, does the gimbal do the normal self-calibration (move around to all sides, then center)?
Try this:
- Turn the aircraft on (do not start the motors, doesn't matter if the props are on or not)
- Pick it and hold it in front of you
- While looking at the camera / gimbal, tip the nose of the aircraft up and down slowly (not too steeply, just enough to observe the camera / gimbal action)
- Do the same thing while tipping the aircraft to each side
When you do step 3 and 4, you should see the camera remain level to the ground.
If it doesn't, then you have a bad aircraft. If you just bought it, return it, but you could try to do a manual Gimbal Calibration (in the DJI GO 4 Gimbal menu).
If the gimbal does seem to be working, but you still can't make it pitch up and down with the remote control gimbal wheel, then you may have a bad remote control. If you just bought it, return it.
Also, you can try to tilt the gimbal from the DJI GO 4 app by dragging on the screen. See 2nd paragraph at the top of page 37 in the owners manual.
Chris