Variable $input of type AddProjectV2ItemByIdInput not provided!

[BatoolMM]

I am trying to automate adding an issues to Projects using GHA

      - name: Add To RSF Programme Management Project
        uses: actions/[email protected]

        with:
          project-url: https://github.com/orgs/aim-rsf/projects/9
          github-token: ${{ secrets.GH_TOKEN }}

I am not sure why it keeps getting this error - I have been trying to debug it for ages, any help is appreciated!

Run actions/[email protected]
##[debug]Issue/PR owner: aim-rsf
##[debug]Project URL: https://github.com/orgs/aim-rsf/projects/9
##[debug]Project owner: aim-rsf
##[debug]Project number: 9
##[debug]Project owner type: orgs
##[debug]Project node ID: PVT_kwDOBlYxfM4AEvO5
##[debug]Content ID: undefined
Creating project item
Error: Request failed due to following response errors:
 - Variable $input of type AddProjectV2ItemByIdInput! was provided invalid value for contentId (Expected value to not be null)

The URL is correct but is it because the project is private?