I ended up opening a SR on this, got the answer from Jay...
This is typical of one of two things...
- There is no master branch present in GitLab for the project.
- The access token is wrong or otherwise invalid.
My issue was #1. While I created the group and project, I did not touch it with git, so no master branch to start off with. A quick "readme.md" file and wham master branch created and content capture is working.