If you see a build failure with:
Cannot find a job named `build` to run in the `jobs:` section of your configuration file. If you expected a workflow to run, check your config contains a top-level key called 'workflows:'
Check how the job was triggered (top right):
username (updated project settings)
This usually means a build was triggered when settings were changed in the UI. If the config includes a CircleCI 2.0 Workflow then it will fail since it tries to run without the context of understanding that it's a Workflow. We're aware of this issue and plan to fix it in the future.
To solve the issue for future builds, push a new commit to GitHub or Bitbucket and the Workflow will run correctly.