I try to run GitLab CI for private GitLab instance with Kubernetes at GCP following this instruction.

I got IP of Kubernetes master with kubectl cluster-info

Then I created ServiceAccount with kubectl, and also get token with command kubectl describe secret/SERVICEACCOUNT-XXXXX

Then I got the certificate with

kubectl -o json get secret SERVICEACCOUNT-XXXXX | jq -r '.data."ca.crt"' | base64 -d - | tee ca.crt

I inserted IP, token and ca.crt content in the Kubernetes integration fields for "Add an existing Kubernetes cluster" command at GitLab.

After that, I tried to install Helm at GitLab, but get an error

Something went wrong while installing Helm Tiller
Kubernetes error: Unauthorized

Can you help me, please, to find out how to solve these problems?