I am trying to copy some files from Firebase into a Gitlab repo.
Using my personal SSH credentials, I am able to do this.
I'd like to use deploy tokens. I generated a fresh token and gave it all the permissions I can. However, when I run the CI pipeline I get an "fatal: Authentication failed"

Gitlab CI Deploy Token cant push to repo
A deploy token is simply not made for that. As per the documentation a deploy token is not capable to write to a GitLab repository. Here is what you can do with a deploy token:

Clone Git repositories.
Pull from and push to a GitLab container registry.
Pull from and push to a GitLab package registry.

What may be a better fit for your use case is a so called Deploy Key. If the deploy key has read-write permissions you should be able to solve your issues.
