Can I ask whether you’re having a private Gitlab repo or one that is hosted on your company’s intranet? Could you try whitelisting Katalon’s domain within the doc below?
If your GitLab is private, I guess it would be difficult to use your GitLab in Katalon Studio Platform Edition backed by TestOps. Why? See the following post of mine:
But I am not sure. I am still waiting for an answer from Katalon team to my question.