A failing GitHub Actions workflow can be due to a variety of reasons, including syntax errors in your workflow file, permission issues, missing environment variables, or uninstalled dependencies. Start by checking the run logs available in the Actions tab of your repository, as these provide specific error messages and indicate where the workflow is failing. If you see syntax errors, review the `.yml` file format carefully to ensure correct indentation and syntax. Permissions errors, especially when using `GITHUB_TOKEN`, often require adjusting permissions in the workflow file under `permissions`. Missing dependencies should be addressed by including `npm install` or relevant commands in the setup steps of your workflow. Lastly, confirm environment variables are set correctly in GitHub's Secrets, as undefined variables can break builds. Each step's logs will help you pinpoint the exact issue, allowing you to fix and re-run the workflow.