No Such Host: Kubernetes/Docker cannot pull from private k8 registry
It seems your private DNS is misconfigured. Check your host or make sure that docker-registry.default is the a valid hostname.
You can run a temporary Ubuntu pod to check if that hostname is resolving correctly from your cluster, e.g.
$ kubectl run ubuntu -it --image ubuntu --rm=true -- bash
root@shell:/# apt update &amp;&amp; DEBIAN_FRONTEND=noninteractive apt --yes install dnsutils
root@shell:/# dig docker-registry.default
docker-registry.default.    IN  A D0.y0u.h4ve.1P?

Additional suggestions:

If you're using a cloud provider (such as Azure), make sure your Private DNS zone is linked with your cluster's virtual network. Read: Connect privately to an Azure container registry using Azure Private Link
If your container registry endpoint isn't correct, edit the deployment manifest and fix the image path.
Test pulling the image from another VM within the same private network.