Gitlab Operator on Openshift fail to create runner pod

My gitlab server is using a self-signed cert.

I followed the steps at to install a runner on Openshift 4.5. The pod of runner failed to start:

$ oc get po
NAME                                   READY   STATUS             RESTARTS   AGE
gitlab-operator-68bddc9f88-b2trd       1/1     Running            0          24m
gitlab-runner-runner-ff84dbc88-7msvk   0/1     CrashLoopBackOff   7          13m

Relevant logs and/or screenshots

The error log:

$ oc logs gitlab-runner-runner-ff84dbc88-7msvk
Registration attempt 1 of 30
Runtime platform                                    arch=amd64 os=linux pid=12 revision=4c96e5ad version=12.9.0
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...                   
ERROR: Registering runner... failed                 runner=9G8ZEKYw status=couldn't execute POST against Post x509: certificate signed by unknown authority
PANIC: Failed to register this runner. Perhaps you are having network problems

Environment description

Openshift 4.5 Gitlab CE 13.3.2

Please help, thanks.