This page described how to configure the pipeline as code for a multi-channel workflow in jenkins.
This is a quote from the description inside:
The Multibranch Workflow feature (provided by the workflow plugin) provides the following key features:
- Automatically create a workflow (work) in Jenkins for a new branch in repo (assuming webhooks are registered from GH to Jenkins) .
- A string specific to this child branch and its unique change and assembly history for scm.
- Automatic cancellation / deletion of a task for branches deleted from the repository, according to the settings.
- The flexibility of customizing branch properties by overriding parent properties, if required.
To set up websites, see this page .
To check if your jenkins are reporting events, you can use this function below: 
PS: look at the URL that you configured, if you omitted the "/" at the end of the URL, it may not be able to reach the jenkins.
Hope this helps!
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