To troubleshoot connection issues with Docker and PSQL, you can follow these steps:

1. Check Docker container logs for any errors or warnings.
2. Verify the PSQL server is running inside the Docker container.
3. Ensure the port mapping is correct between the host and the Docker container.
4. Test the connection using the PSQL client from the host machine.
5. Check for any firewall rules blocking the connection.
6. Review the Dockerfile and Docker run command for any misconfigurations.

By following these steps, you can identify and resolve the connection issues with Docker and PSQL.