"Branch not found" backend error persisting despite attempting solutions on forum

I am trying to set the branch in the backend of via the config.yml file. When I set branch to either master or dev-branch, the two branches in my GitHub repo that I’m working with, trying to access the CMS through “/admin” results in a Branch not found error. I’ve given auth access to my organization through my GitHub settings. “dev-branch” is the branch that I’m currently using to deploy on Netlify and it still doesn’t work. The only “branch” value that works is “main” (I don’t have a “main” branch on my repo), and once I get into the CMS none of my YAML fields are rendered, just the default view.

Here is my relevant config.yml code:

name: git-gateway
branch: main # Branch to update (optional; defaults to master)

Hey, do you happen to have a link to the repo if it is public, or for a Support Engineer to help an App Id or domain would help.