Jupyterhub Oauth2 DockerSpawner /user/[name] 404

container is runing

Please share your configuration and logs from both jupyterhub and the user container (jupyter-sunn65156).

My first suspicion is that the URL is not actually correct - it should end with /user/sunny5156/ (trailing slash is required), but would need more information (likely a 302 redirect in the logs) to see where the URL is getting produced without its trailing slash.