Services are one-to-one to containers. Therefore, verifying that all major containers are up and not restarting or failing is a good first step. In a terminal, run: 
docker ps
You should see output similar to the following:
It is important to note that each container appears in the output:
  • Installer_repo_api
  • Installer_nginx_proxy
  • Installer_repo_worker
  • Installer_repo_dispatcher
  • Installer_repo_proxy
  • Installer_keycloak
  • Installer_postgres
  • Installer_redis
It is also important to note that the status of each container is Up, and that it does not get stuck in a restart loop. Finally, you should be able to use a browser to navigate to the domain that you supplied when executing the installer. If you are able to successfully authenticate and use the product, it has installed correctly.