I followed this guide to push a docker image to my Google Cloud Container Registry. However

docker push eu.grc.io/<project-id>/<image>:<tag>

only returns

The push refers to repository [eu.grc.io/<project-id>/<image>]
Get https://eu.grc.io/v2/: dial tcp xx.xx.xxx.xx:443: connect: connection refused

Has anyone encountered this error before or knows how to get it working? I'm seriously out of ideas, there may be something wrong with my network configuration but I'm not familiar enough with that side of Ubuntu to know what I should be looking for. For context, I've set up a kubernetes cluster for hosting jupyterhub following this guide.

I can run the image locally, gcloud info returns all the correct info and gcloud auth configure-docker returns credential helpers already registered correctly.

Additional Info:

Ubuntu 16.04

gcloud version
Google Cloud SDK 214.0.0
bq 2.0.34
core 2018.08.24
gsutil 4.33

docker version
Version:           18.06.1-ce
API version:       1.38
Go version:        go1.10.3