I kept getting the error message "TF401180: The requested pull request was not found." even though it worked fine locally using my own PAT token.

I am trying to check the status of a PR in a remote repo hosted in Azure DevOps while running a pipeline from a different repo in the same org and same project. I am using the access token of the pipeline, and the Build Service has permissions on the remote Git repo.

You can either turn off the protection for "Protect access to repositories in YAML pipelines" or review this documentation to understand it better: Secure access to Azure Repos from pipelines | Microsoft Docs.

It is probably a better option to simply checkout that other repo in your pipeline to ensure that your access token is scoped for that repo too.