Runner 404 not found

I installed Gitlab via Gitlab’s helm chart using Helm 3.0.1 on a 1.15.6 kubernetes cluster.
I can access my gitlab instance at but my runner is crashing with the following logs:

ERROR: Registering runner... failed runner=h8dHL-_z status=404 Not Found
PANIC: Failed to register this runner. Perhaps you are having network problems
Registration attempt 7 of 30
Runtime platform arch=amd64 os=linux pid=100 revision=577f813d version=12.5.0
WARNING: Running in user-mode.
WARNING: The user-mode requires you to manually start builds processing:
WARNING: $ gitlab-runner run
WARNING: Use sudo for system-mode:
WARNING: $ sudo gitlab-runner... 

I also have some time an error about SSL certificate signed by unknown authority:

ERROR: Registering runner... failed runner=h8dHL-_z status=couldn't execute POST against Post x509: certificate signed by unknown authority

I tried to access on my browser and I don’t have any issues but the file is empty.

Can someone help me with this ?