Using Gitlab with private Github project

I have a private Github project within an organization. When I import the project into Gitlab just for CI/CD I can see within Github that the webhook is firing and being received correctly however in Gitlab it gives me an error in the mirroring section saying gitlab fatal could not read username for no such device or address.

Has anyone come across this before?

I really want to show my company how this can work but it’s getting really frustrating.