Docker Python container didn't respond to HTTP pings on port: 8000 on Azure

this container works perfectly locally, but when uploading it on azure this error occurs, I already set WEBSITES_PORT=8000 env, and still getting this error:

ERROR - Container menbeerdemo2021_0_fdd36c41 didn't respond to HTTP pings on port: 8000, failing site start.

here is my dockerfile:

FROM python:3.8

EXPOSE 8000
ENV LISTEN_PORT=8000

COPY . .

RUN apt-get update
RUN pip3 install -r requirements.txt

CMD [ "python", "app.py"]

docker-compose.yml:

version: '3.5'
services:
  menbeer_web_backend:
    image: menbeerdemo2021.azurecr.io/menbeer-web-backend:latest
    build: .
    ports:
      - "8000:8000"