depthai-sdk visualize does not show window

i'm running the demo code

from depthai_sdk import OakCamera

with OakCamera() as oak:
    color = oak.create_camera('color')
    human_pose_nn = oak.create_nn('human-pose-estimation-0001', color)
    oak.visualize(human_pose_nn)
    oak.start(blocking=True)

the output looks normal:

 python ./depthai-sdk.py
/Users/abc/.local/lib/python3.8/site-packages/depthai_sdk/oak_camera.py:237: UsbWarning: Device connected in USB2 mode! This might cause some issues. In such case, please try using a (different) USB3 cable, or force USB2 mode 'with OakCamera(usbSpeed=depthai.UsbSpeed.HIGH)'
  warnings.warn("Device connected in USB2 mode! This might cause some issues."

However, no window shows up - what can i do? Thanks

conda environment:

blobconverter==1.4.2
boto3==1.34.23
botocore==1.34.23
certifi==2023.11.17
charset-normalizer==2.0.12
depthai==2.21.2.0
depthai-sdk==1.9.4
distinctipy==1.3.4
idna==3.6
jmespath==1.0.1
marshmallow==3.17.0
numpy==1.24.4
opencv-contrib-python==4.5.5.62
packaging==23.2
python-dateutil==2.8.2
pytube==15.0.0
PyTurboJPEG==1.6.4
PyYAML==6.0.1
Qt.py==1.3.8
requests==2.26.0
s3transfer==0.10.0
scipy==1.10.1
six==1.16.0
types-pyside2==5.15.2.1.6
urllib3==1.26.18
xmltodict==0.13.0