Q:

Git: can't push changes after changing push URL in Visual Studio

So, I have a project in Visual Studio connected to Git source control (I have a repo on GitLab).  Now, I want to create another project on GitLab and push my existing project there.  
I have created a new empty project in GitLab, and tried to simply change the push URL in Visual Studio to the URL of the new project (Settings - Repository Settings - Edit push URL) and then push my changes, again through VS.  However, this didn't work, I got the infamous 

refs/heads/master, pre-receive hook declined

This seemed like a simple way to do this, but now I'm guessing I need another method. 
Note: the master branch is not protected. 

A:

After trying several other methods (and failing), I have discovered the problem: I couldn't push because, for some morbid reason, I was not a member of the project I have created on GitLab...

