Error in installing JupyterHub using Kubernetes and Helm

Summary:

I've followed this guide as a means of installing JupyterHub onto my OCI instance. https://zero-to-jupyterhub.readthedocs.io/en/latest/

Unfortunately, I've encountered an error that I'm not sure how to solve.

Content (required):

After installing Helm, I've performed the following steps:

helm repo add jupyterhub https://jupyterhub.github.io/helm-chart/
helm repo update
vim config.yaml # and added the comments to it as per the guide
helm upgrade --cleanup-on-fail \
 --install installation-name-0 jupyterhub/jupyterhub \ 
 --namespace kubernetes-namespace-0 \
 --create-namespace \
 --version=1.2.0 \
 --values config.yaml
Error: Kubernetes cluster unreachable: Get "http://localhost:8080/version?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused

Version (include the version you are using, if applicable):