Push (Mirroring) whole project to a blank project

I have an existing project in my Gitlab CE which I want to create mirror at Gitlab.com.
The problem is this project was not created (cloned) from Gitlab,com.
I created a new blank project in Gitlab.com, & pushed from my Gitlab CE. But this doesn’t work. No file is added to project at Gitlab.com.
How to create the mirror?

Someone had a similar issue, when wanting to push to github. I expect you have your gitlab url without your username, but you don’t post many details or errors, so difficult to say. Follow my post here it should help you get it working:

I found that the problem is due to the main branch is protected. It worked after unprotect it. Thanks.

Did you create the project and initialize it with a README.md? Usually if you are going to push to it yourself, you just create an empty project that wouldn’t have any branches. That way the issue shouldn’t occur. I created an empty project, no branches, no initializing since I was going to mirror it later, and this problem I didn’t have. So I expect it was due to this.