I am trying to run my react frontend project on localhost:8000 with a docker-compose yml. And I am encountering a ERR_EMPTY_RESPONSE

Here is my docker-compose.yml

version: '3.8'

services:
  app:
    build: .
    image: bookdup/website
    depends_on:
      - redis
    environment:
      - REDIS_HOST=redis
      - REDIS_PORT=6379
    ports:
      - "8000:3000"
      - "8001:8001"
    networks:
      website-demo:
        aliases:
          - website-server
    volumes:
      - .:/app
    command: ["supervisord", "-c", "/etc/supervisor/conf.d/supervisord.conf"]

  redis:
    image: redis:latest
    container_name: redis
    ports:
      - "6379:6379"
    networks:
      - website-demo

networks:
  website-demo:

Here is my DockerFile

# Use a suitable base image, e.g., Ubuntu
FROM ubuntu:latest

# Install necessary packages
RUN apt-get update && 
    apt-get install -y nodejs npm python3 python3-pip python3-venv nginx supervisor

WORKDIR /app

COPY ./backend /app/backend

RUN pip install -r /app/backend/requirements.txt --break-system-packages

# Copy and install frontend requirements
COPY ./frontend /app/frontend
WORKDIR /app/frontend

# Update the start script in package.json
RUN sed -i 's/"start": "cross-env PORT=8000 react-scripts start"/"start": "react-scripts start"/' package.json

RUN npm install

# Set working directory back to root
WORKDIR /app
COPY credentials.json /app
COPY .env /app
COPY service.json /app

# Copy supervisord configuration
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf

# Set environment variables
ENV PYTHONUNBUFFERED 1

# Command to run supervisord
CMD ["supervisord", "-c", "/etc/supervisor/conf.d/supervisord.conf"]

I have tried two similar questions and none have worked for me

1. localhost didn’t send any data. ERR_EMPTY_RESPONSE nodejs
2. This page isn’t working localhost didn’t send any data. ERR_EMPTY_RESPONSE

Any help is appreciated