Configure SAST failure

We have a CE GitLab on premise CE 15.0
I discovered the “security testing”, where we can do a “static application security testing” on project.

So, on a project, in the security configuration projectUrl/-/security/configuration? there is a “Static Application Security Testing (SAST)” group, that was "Not Enabled’, in that we have a button named “Configure with a merge request”.

When clicking on that button, a red notification appears in the top on the window “A file with this name already exists”

what does it mean and how to get rid of this?