no live upstreams while connecting to upstream

I am trying to run an image using the nginx-proxy image. I created the following docker-compose.yml file to make executing the commands easier

version: '3.4'
services:
  nginx-proxy:
    image: jwilder/nginx-proxy
    container_name: nginx-proxy
    ports:
      - 80:80
      - 443:443
    restart: always
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - /etc/certificates:/etc/nginx/certs

  private_package_name:
    image: crestapps/private_package_name:latest
    container_name: private_package_name
    command: tail -f /dev/null
    environment:
      - VIRTUAL_HOST=private_package_name.crestapps.com
      - VIRTUAL_PORT=51736
      - ASPNETCORE_ENVIRONMENT=Development
    ports:
      - 51736:80
      - 44344:443
    volumes:
      - /app/storage:/storage

When I run docker-compose up, both apps run as expected. However, when I make a request to https://private_package_name.crestapps.com I get

502 Bad Gateway

When I look at the logs I see the following

nginx-proxy          | nginx.1    | 2020/01/20 23:49:40 [error] 42#42: *1 no live upstreams while connecting to upstream, client: PersonalIpAddress, server: private_package_name.crestapps.com, request: "GET / HTTP/2.0", upstream: "http://private_package_name.crestapps.com/", host: "private_package_name.crestapps.com"
nginx-proxy          | nginx.1    | private_package_name.crestapps.com PersonalIpAddress - - [20/Jan/2020:23:49:40 +0000] "GET / HTTP/2.0" 502 157 "-" "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:72.0) Gecko/20100101 Firefox/72.0"
nginx-proxy          | nginx.1    | 2020/01/20 23:49:41 [error] 42#42: *1 no live upstreams while connecting to upstream, client: PersonalIpAddress, server: private_package_name.crestapps.com, request: "GET /favicon.ico HTTP/2.0", upstream: "http://private_package_name.crestapps.com/favicon.ico", host: "private_package_name.crestapps.com"
nginx-proxy          | nginx.1    | private_package_name.crestapps.com PersonalIpAddress - - [20/Jan/2020:23:49:41 +0000] "GET /favicon.ico HTTP/2.0" 502 157 "-" "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:72.0) Gecko/20100101 Firefox/72.0"

When I execute docker ps I get the following

CONTAINER ID        IMAGE                                COMMAND                  CREATED              STATUS              PORTS                                           NAMES
d661d4bff1f3        crestapps/private_package_name:latest   "tail -f /dev/null"      9 seconds ago        Up 6 seconds        0.0.0.0:51736->80/tcp, 0.0.0.0:44344->443/tcp   private_package_name
0bd0da4141f8        jwilder/nginx-proxy                  "/app/docker-entrypo…"   About a minute ago   Up About a minute   0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp        nginx-proxy

running docker logs nginx-proxy gives me the following

WARNING: /etc/nginx/dhparam/dhparam.pem was not found. A pre-generated dhparam.pem will be used for now while a new one
is being generated in the background.  Once the new dhparam.pem is in place, nginx will be reloaded.
forego     | starting dockergen.1 on port 5000
forego     | starting nginx.1 on port 5100
dockergen.1 | 2020/01/21 00:00:51 Generated '/etc/nginx/conf.d/default.conf' from 2 containers
dockergen.1 | 2020/01/21 00:00:51 Watching docker events
dockergen.1 | 2020/01/21 00:00:51 Contents of /etc/nginx/conf.d/default.conf did not change. Skipping notification 'nginx -s reload'
2020/01/21 00:01:08 [notice] 53#53: signal process started
Generating DH parameters, 2048 bit long safe prime, generator 2
This is going to take a long time
dhparam generation complete, reloading nginx
dockergen.1 | 2020/01/21 00:02:27 Received event die for container 274d6e739fd8
dockergen.1 | 2020/01/21 00:02:29 Received event stop for container 274d6e739fd8
dockergen.1 | 2020/01/21 00:02:29 Generated '/etc/nginx/conf.d/default.conf' from 1 containers
dockergen.1 | 2020/01/21 00:02:30 Contents of /etc/nginx/conf.d/default.conf did not change. Skipping notification 'nginx -s reload'
dockergen.1 | 2020/01/21 00:02:33 Received event start for container d661d4bff1f3
dockergen.1 | 2020/01/21 00:02:33 Generated '/etc/nginx/conf.d/default.conf' from 2 containers
dockergen.1 | 2020/01/21 00:02:33 Running 'nginx -s reload'

running docker logs private_package_name gives me nothing.

Is there something I am doing wrong here or is this some sort of a bug? Help would me much appreciated.

[hacker-h]

The VIRTUAL_PORT has to match the port within your target container (80 in your case). It has nothing to do with the port mappings you declare using the ports list, you do not even have to do any port mappings if you want to access your container merely via proxy.

[Lilja]

I had the same issue and I added EXPOSE <port> to my Dockerfile, it worked thereafter.