The 'remote: Repository not found' error during a `git push` typically results from an incorrect repository URL or a permissions issue. First, confirm that the remote URL matches the repository’s actual URL by running `git remote -v`. If you detect an error, update the URL with `git remote set-url origin `. If the repository is private, you’ll need to authenticate by either configuring a personal access token (PAT) or using SSH if SSH access is set up. Ensure that the URL format aligns with your access method, either HTTPS or SSH, and that you’re authenticated. For HTTPS, replace password with a PAT, as GitHub no longer supports password authentication for private repositories. If everything is set up correctly, a push should succeed without further issues.