Unable to deploy to Digital Ocean Kubernetes using GitLab CI

I’m moving my review apps from Google Kubernetes to Digital Ocean Kubernetes.

I have succesfully linked the Kubernetes clusted to GitLab. I have installed Helm Tiller, Ingress, Cert-Manager, and Prometheus using the GitLab integration. I have upgraded Tiller to the latest version manually, as did I on the previous Google cluster.

The cluster is RBAC-enabled,GitLab-managed, configured to use the default namespace, and tied to the * wildcard environment scope.

Now my deployments are failing. job output

$ helm upgrade "$CI_ENVIRONMENT_SLUG" config/charts/appsemble-docs --atomic --install --set "git.commit.sha=$CI_COMMIT_SHA" --set "image.tag=$CI_COMMIT_REF_NAME"
Error: pods is forbidden: User "system:serviceaccount:default:default-service-account" cannot list resource "pods" in API group "" in the namespace "gitlab-managed-apps"

Manual deployments on my own laptop work fine.

What could be causing this issue?

I asked the same question on the Digital Ocean forums and got an answer there.