Get_rgba returns empty numpy array

Omniverse Isaac Sim
1

I create a new stage in isaac sim using omni.usd.get_context().new_stage(). I then populate the new stage with many prims using the USD api. From there, I create a new camera as such:

camera = Camera(
            prim_path=camera_prim,
            resolution=DEFAULT_RESOLUTION
        )
camera.initialize()
camera.set_focal_length(1.0)

After creating the camera, I also wait some frames before calling camera.get_rgba() as suggested here: Empty ndarray is returned from camera.get_rgb() on IsaacSim API - #2 by altick. However, I am still getting am empty array when calling get_rgba. Is there anything I am missing on my side? I need to render the image and get the image as a numpy array. Here is the config I am using for the setting up the SimulationApp:

simulation_app = SimulationApp({
    "headless": True,
    # "hide_ui": True,
    "width": 1080,
    "height": 1080,
    "renderer": "RayTracedLighting"
})